The Boosters are available the next day after you purchased one of the three offers.

I had the same issue on Mozilla, and was told by help support to switch my default browser to Google Chrome which sorted the issue for me. If you already set your default browser to Chrome, try clearing your cache. You can also try entering the game through these links:
 https://tankionline.com/play/?resources=https://s-ar.eu.tankionline.com 
 https://tankionline.com/play/?resources=https://s-kg.eu.tankionline.com
https://tankionline.com/play/?resources=https://s-de.eu.tankionline.com
https://tankionline.com/play/?resources=https://s.eu.tankionline.com
Someone also provided this solution for client so you might give it a try.
 

You do not claim them, they will be automatically added to your account, whenever their are ready to be distributed. There is no specific time given for this. The announcement only states that the rewards will be added after the end of the event.

It should not take more than week. I believe someone mentioned somewhere they do not actually work on weekends, so since the challenge ended Friday/Saturday, you will most likely have to wait for next week for the rewards to be added to your account.

1. Challenge Accepted will end at the end of the current month, from 1st of February a new one will start. The prizes are distributed usually within a week from the end of challenge.
2. Early access works similarly as Product Kits, it does not matter what your previous modification of that equipment is, it will give you the modification you purchased directly.

From my experience, it usually was added within a week from end of the challenge.

Rank up reward has been changed in update 675 (January 2022). The rank up reward is now always 1 Regular container regardless of what rank you reach. You can claim the container in special missions section.

They used it as a promotional prize back in the day when they also made contests distributing computer accessories with partnership of Canyon company. My best guess is that their partnership with Canyon ended and the paint initially trickled down to containers. It seems that in 2021, they eventually decided for some reason that it should be discontinued. Perhaps, it was deemed by them not interesting for container pool, perhaps they shelved it for potential future collab. That's up for a speculation. It's hard to say whether it will ever reappear, it seems that it is a very specific paint tied to specific events, so I dont see it returning unless those specific events (collab with Canyon )reoccur again.
But, its Tanki, you can never be sure.

Just click on your rubies right over the crystals:
→  
it will automatically take you to a converter where you can choose the amount of tankoins you want to change to rubies.

Once you bought the event pass, you will start  receiving missions that you need to complete to get the event currency - ice coins. Every day for the duration of the event one new mission will appear in the freezer games section that you need to complete and claim.

This way you can earn a maximum of 13 coins. You can also buy additional coins in the shop under the ICE COIN subsection for crystals or rubies.
 

That is actually a very bad idea. First, it promotes the very act of sabotage as something legal and "good" which only leads to more people sabotaging and doing it even without the use of grenades. It also creates a lot of bad blood between players which leads to more personal conflicts and more sabotage. People start sabotaging back and it creates endless vicious circle of more and more sabotage that heavily distracts from actual gameplay.
Additionally, the problem isn't in the camper players themselves. Camping existed from the very beginning of the game. Tanki even created turrets like Shaft and Railgun that are more or less for ages camper turrets, along with many more that can be to extent used for camping.
The problem is in gameplay itself:
a) Tanki failed to introduce effective anticamping options. Stuff like Magnum and Striker that have been advertised as anticamping new options have  become some of the most effective camping turrets themselves.

b) Gameplay heavily shifted away from battle objectives. Completing battle objectives is one of the main stimulants for players to not camp. Apart from TDM, most other game modes require you to move around the map to actually complete the battle objective - you need to move to capture flags, to deliver the rugby ball, to capture the points, etc..
However these days, completing battle objectives either outright does not give enough points to justify playing it (like after the score nerf, delivering flags in ASL), or even if the battle objectives do give quite good amount of points (like for delivering flag in CTF), you can still outperform players who are completing battle objectives by simply camping or playing every mode as a deathmatch, because a lot of equipment these days gives you more points than doing something useful like capturing flags, or delivering balls. For example, in my opinion, destroying an enemy should give far less points (excluding TDM) than something like delivering flags or rugby balls, These modes should be focused more on objectives and give far more points for succesfully completing them.
On top of all of this, completing battle objectives has been far less important because winning or losing is no longer important for getting good rewards after the battle. You can lose 6-0 in CTF and still get more crystals than the winning team just because you have some busted augment that gives you more points than players on the winning team gained from capturing flags. And of course, missions and special missions which is the sole reason some players even play the game daily, rarely have any focus on battle objectives these days.
c) A lot of people camp because they cant do anything else in battle.  There is still a big imbalance between equipment of f2p and buyers. Lot of people cant leave the safety of their base, because the moment they leave, they get picked up by enemy campers or busted augments that kill them in nanoseconds. Some people simply dont have the skills or equipment to keep up with more powerful equipment of buyers or endgame players. So they stay in the safety of bases that often provide the power in numbers and camp because it is the only thing that somehow gives them a fighting chance.

You can try using the form for restoring access to your account, or you can check this page for information on how to contact them through email.

Some of the best augments rn are Striker exotic augments like Vacuum, Faust, Tandem, then Large Caliber Vulcan, Critical Mix Firebird, some Pulsars like Smoky, Firebird, Tesla, Freeze, Plasma Turbo Accelerator Twins, Hyperspeed augments, Healing Augments for Thunder and Shaft. Those are some from the top of my head that are either game breaking or performing practically constantly very well. Unfortunately most of these are exotics or legendary augments that are quite hard to come around, you usually have to participate in events to get these which oftentimes comes with a price. However there are also many garage augments that can still perform above average - my personal favorites are Shock Freeze, Incendiary Mix Firebird, Plasma Torch Rico, Heavy Capacitor Shaft among others that are still very much usable depending on your skill.
As for Blaster, Lifeguard and Miner, they are now hull augments and quite powerful ones, especially Blaster and Lifeguard replaced many AP and EMP immunities as top choices. They can be rarely obtained from containers as legendary drops and sometimes appear as prizes in events as well.

Helios is a paint reserved for members of the Creative League. To receive it, you have to become a member of the Creative League and earn it afterwards by presenting continuos good art over a certain period of time. You can check the Creative League Forum Topic for more information.

For in game clans:

Click on the icon in the circle, there you can click "Join another clan". Then a window will pop out with "Requests" and "Invitations". In the requests, you can use the search bar to find the clan you want to join and send them request. Obviously it is up to them whether they want to accept you or not.
As for tournament esports teams, I saw you already added yourself to the list of players who are looking for a team. You can also check the clans with empty spaces under recruitment subsection, click on them and apply for the team. Once again, its is up to the team whther they want to accept you or not, and they might try out your skills in battle.

If you catch a regular Gold Box, you will receive 1 000 crystals. Tankoins are usually not present in Gold Boxes and if they are, it usually is in very specific small amount like 15 Tankoins Gold Box. The crystals are automatically added to your Crystal amount. If you have a Gold Box supply, and you want to drop these for yourself, it is best to create a private pro battle with supplies allowed and drop them in that battle. If you are not sure what key is assigned to your Gold Box Supply, you can check Settings - Controls - Overdrive and Supplies.

Everything was killed off in 2021 - 2022 along with Newspaper, Contests Team, Events team and for better or worse Parkour. It almost feels like everything that provided some sort of competition for extra rewards was closed and disappeared in an instant for what I suppose is low engagement due to the fact how Tanki lost majority of its community. However, I am not sure there ever was any official statement made and, if there was, it was lost to time.
As if they come back, who knows, but I am super pessimistic about it.

It has been mentioned in the work-in-progress wiki: https://en.tankiwiki.com/Development_Plans and I am pretty sure it has been asked in vlog some time ago, but as far as I know, there hasn't been any specific date of release of this future. But I believe they will sooner or later introduce this future back, as it is potentially another source of income for them, as they plan on selling premium animated gifts for premium currency (tankoins most likely)

These are the approximate dates released on the tournament page:
 
The approximate dates of the Summer Major 2024 stages:  
Challengers stage: 1st Round: May 16th; 2nd Round: May 18th; 3rd Round: May 20th and 21st; 4th Round: May 23rd and 24th; 5th Round: May 26th and 27th.  
Legends Stage: 1st Round: June 4th; 2nd Round: June 6th; 3rd Round: June 8th and 9th; 4th Round: June 11th and 12th; 5th Round: June 14th and 15th.  
Champions Stage: Quarter-final matches: June 23rd, 24th, 25th and 26th; Semi-final matches: June 27th and 28th; Match for 3rd place: June 29th; Grand Final: June 30th.
 
You can expect Tanki fund to take place somewhere around this time.

Hydra is currently classified as an Exotic augment for Striker, which means it is extremely difficult to obtain it. Afaik, it isn't currently available in any way. The only way to obtain it will be through either Ultra containers  if the developers will make it obtainable in them again (which will obviously be a very minuscule chance) or through some Tankoin pass event like Snowtrap, Halloween trick or treat type of thing. In any way, given that it is exotic item, the chances for f2p players to obtain it are fairly small.

Personally, havent noticed anything of this sort. Might have been some temporary bug or mistake. As far as I know, gingerbread was used as a currency in "The Tanki and the Snow trap" minigame which was basically the winter equivalent of Halloween minigame: https://tankionline.com/en/2023/01/the-tanki-and-the-snow-trap-mini-game/
Possibly, it might have been a bug that leaked  some sort of spinoff of the event that might be in the works after the Tanki Fund, but we will need to wait for the official announcement for confirmation on that.

Hey. No, containers dont have an expiration date. Once you receive them, they will stay in your garage forever, and will be turned to old containers when the items in the pools get updated.
However, containers system will be changed in the upcoming months, and the they will be changed to keys. This means that containers will either be transformed to keys, or if you did not consent to the 10:1 transfer rate, they will be forcefully opened. You can read about it here: https://tankionline.com/en/2023/09/container-system-update/

Yes, they have been removed with Patch Update #721  released 14th April 2023.

I believe the site refreshes every hour, just like with Assemble the Tank event, I believe it once took two hours actually for me to refresh in the previous event, so I would wait at least an hour before checking your current amount of bullets. 

Hey. The tankoins have not been a guaranteed prize for every player, only a certain percentage of players have been randomly generated from the poll. If you did not receive tankoins, it is most likely due to your accounts not being on this winner list.
To participate you had to purchase one of the offers available at the time. Are you sure you purchased one of the "Essentials", "Backup Vault", or "Spectacular Appearance" offers.
Check properly if you dont have one of the Pulsars like Isida, Railgun, Vulcan or skins like Dictator GT on your account, or whether your containers amount increased.
If still not sure, contact support service, here are the forms you can contact them with: https://en.tankiwiki.com/Technical_Support?attempt=1
They will be able to tell you whether you participated or not, or if some error happened on their part when prizes have been distributed.