Forum

1.I think you mean you want to know where or not someone is banned for cheating(not 100% sure though). If that's the case, then:
If a player has been caught cheating on Assist, he wont be playing and you can't see him (on that account at least)
If you wish to see history/other accounts of player, go to http://history.anticheatinc.com/aa2/ . Although I must warn you it's no longer up to date (only accounts since before 2012 I guess).
If you really think that someone is cheating, you can post it here on the forums (or send a PM to Sergio) and it will be looked into. (Don't do it too often though, Sergio can't devote all his time on this game)

2.There will almost always be some cheats/hacks that are not detected right away. That's why all the anticheat software always need to evolve.
The bottom line is that if you're not physically next to the person, you can never really say with 100% certainty that they're not using something.