1. You must be over 13 to use this site 

what age old must be to can play CC

From Classicube TOS:
"b. Your account must follow these guidelines, or it may risk being deleted, disabled, or banned:

• User account names must be non-offensive
• User accounts must not be used to spam or perform malicious actions
• User accounts names must not purposefully be exactly the same as Mojang employees' account names
• The account registrant, owner of the account, or entity that will be using the account must not be under the minimum age requirement of 13 years."

"Singleplayer does not require an account to play, and therefore can be played by Players aged under 13 years of age as long as they do not login to an account and have permission from their parent or guardian to play."

TL;DR:
You can only have an account if you are 13+. But if you are under 13, you may only play singleplayer without an account, and with parent permission.

good (i have 13) :)