You can collect them anytime between 24 hours but first you will have to visit the >>Special<< tab in the Missions on HTML5 for the 24hrs time to start. If you don't, they will disappear in a few hours and you won't be able to claim it.

Emil is right, but here is a bit detailed answer from my side too! ?
The Eternal-loading is a common issue, you can try the following to solve this problem.
Clearing the Client/Browser cache: Clear Client Cache, Clear Browser Cache. Uninstalling and Re-installing the client. Checking your Internet connection. The problem may also arise if your internet connection is unstable, you may reboot your internet modem if necessary. You can check your Internet speed here.

Hello,
Have you tried uploading the image(s) to a 'Hosting website' before attempting to post the image in the Forum? Please refer here if you're unsure: How to upload an image to a hosting website

Hello,
Mobile or desktop, doesn't really matter when it comes to opening containers. Just like opening containers together or separately doesn't change the rarity of the items you receive, TO mobile doesn't do any difference either. The talks about this in the forum are not true.

Hello,
Check if the nickname of the account you're talking about is correct, also check if the nickname was changed due to inactivity. Please refer to this wiki article to understand how nicknames are changed when an account is inactive. If your account is not connected to an e-mail, contact Tech Support using this free form. Otherwise, try to retrieve your account's nickname or password at the login section of the game.
If you believe your account has been blocked by mistake, please contact Tech Support via this free form link.
If you have any other problems regarding your or your friend's account, please contact Tech Support through the respective forms.