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Unfortunately, this is currently only true for small amounts. Theoretically, you can use any amount, but I'm sure that most casinos will ask for KYC (at least if you win and try to make a withdrawal) so you should always be prepared for wasting time on this procedure plus being able to pass KYC - if you are under 18 or gambling is prohibited in your country, then you need to have a fake identity in advance.
Currently, gambling sites are indeed required to do KYC, but there are also those that do not require their users to do KYC, for example, Gamdom
other than that the KYC that is required is usually KYC level 1 and it's not that complicated (compared to KYC levels 2 and 3) so it's not that hard right now