Normally games shouldn’t allow players on different versions to connect to each other. Version checks may be something devs need to explicitly implement, but surely most games should already have them or else I have questions for the developers.

Also, in the context of fighting games specifically, this is largely a nonissue. Fighting game netcode works by sending button inputs only, and the other client will play back those inputs to independently verify the outcome. There’s very little cheaters can try to do that won’t just result in a desync. To my knowledge there’s only ever been one cheating scandal in the FGC, and the accused turned out to be innocent in the end.