1. Do you have implemented a system to prevent multi accounts registration?
We have seen cases where casinos claim that a user tried to double spend or deposit/withdraw and thus the casino blocked the account and froze user fund.
Multi-account registration and preventing double spend attacks are totally two different things. One can be prevented by validating email/username/ip and other by verifying or accepting deposits after a certain number of confirmations. So you can't really put them again in the same sentence since they're not co-related.