Nobody know if an event like Marathon X will be held again. Marathon X was held in order to celebrate Tanki's 10th birthday, which is something big and special so I wouldn't expect to see anything like it soon. Either way, you can follow the News and Announcements in case a contest like this is being announced.

Support nanobots is an augment (alteration) for Isida, it improves healing in exchange for lower damage. You can find it in your garage
Flash:
HTML5:
More details can be found on the Wiki.

Hi, it's hard to tell when new updates are coming. I'd recommend you to follow the Web Version Patch Notes as well as the Mobile Version Patch Notes.

The server crushed/went down. It's fixed now.
Closed.

The server crushed/went down, but you should be able to login normally now.

There were 70 tiers, you can check it in the Challenges Archive as well as in the answers for the Tanki Quiz.

There were 7 honorable mentions for the 'Digital Coloring'  category and 2 honorable mentions for the 'Coloring by Hand' category. You can find the winners and the honorable mentions here.
Answered, closed.

The results have been posted, you can find them here.
Answered, closed.

Please follow the Tanki Quiz topic, you will be notified there once all prizes have been sent out.

Update: The results have been posted, you can find them here.
Answered, closed.

Usually, contests are being announced over the Contests section, the Newspaper section and the News and Announcements section, so you might want to follow these sections to be aware of any contest. As of now, you can participate in the following contests;
 

Your topic will be approved after one of the section curators reviews your idea. I'd recommend you to read the Guide for posting ideas.

Hi, I understand your frustration but you have to understand that the contest team received a huge amount of entries. Therefore, it takes a lot of time to check them all. As for the prizes, it's impossible to give so many players a huge amount of crystals, containers and premium. That would ruin the game's economy. For further reference, check this post.
Please follow the Tanki Quiz topic for updates.
Closed.

Hi, you are allowed to re-submit your entry.

As long as you don't hold a helper position you are allowed to participate. So yes, retired helpers are allowed to participate in events.
But, being a helper you are allowed to participate in some "events/contests" such as Master Of Parkour. You will be informed more about this once you get selected to become a candidate.

There are some augments which can be bought with crystals. Yet, the augments which are purchasable with tankoins cannot become purchasable with crystals.

Cold Resistance protects your tank from the effect of cold, making it harder to slow your tank down. You can find it in the garage, click on the hull you got the augment for and click on "alterations" 
HTML5:
Flash:
Additionally, you can find more information over the wiki.

The rating page is planned to be updated, yet, the developers are focusing on more urgent things such as fixing bugs and improving the HTML5 version of the game.

If you play via a browser, try clearing your browser cache. ~ How to clear your browser’s cache?
If you are using Tanki's client, try clearing your client cache. ~ How to clean Tanki Online clients cache?

The prizes are supposed to be given out this month. Please check the following post for more information;
Please use Contests Feedback/Suggestions/Discussion for other contests related questions.

You can check the Full List of Annual Sales and Events

The players you have seen may have purchased a M2 kit before the modification update and fully upgraded the combo. Other than that, MK7 kits are available for tankoins from the rank of Lieutenant Colonel which is only 1 rank above Major.

Hi. As stated in the Wiki, clan profile customization doesn't work on the client, only in Standalone Flash Player and browser (flash). 
I tried it myself, and the first code works perfectly fine in Standalone Flash Player. I suggest you to download it and customize your clan profile to your liking.
 

It's just about luck, there isn't a method or a secret to get better items from containers.
Answered, closed.

Your account was duplicated due to a bug, you should contact @Maf and he'll sort it out.