First of all, if you familiarize yourself with what can make them freeze your account you will have an idea of what to do to prevent that. Mostly it will have to do with violation of terms. Probably if they find your activities suspicious.

With regards to KYC almost all exchange require KYC for withdrawal of large amounts. You can trade and withdraw freely without having to pass KYC. I will recommend https://changenow.io/ which is an instant that requires no account creation and KYC making you exchange operations anonymous. You can exchange small amounts and there is no upper limits on exchanges.