we start with my question, is it possible if we join bounty without us caught, if we pakek 2 account or more
Don't be so greedy. There are plenty bounties you can join, if you see good project let others to join it too.
If you get caught your account will be marked as scammer. You can use your alt account to enroll different bounties but don't even think about joining the same bounty with all your accounts.