Can be freezed? Should i use them and worry about ?
If you are a criminal, you should worry upon sending your stablecoins to centralized exchanges.
Even If my crypto wallet or exchanger not involved in any bad activities so why someone can freeze basicly to steal my money ?
If the source is from "dirty" activities, there's a tendency that your USDT might be frozen and take note that it's not only the USDT itself can freeze your money but the exchange where it is sent, you are at their mercy. And about those dirty activities, it varies on how the exchange you've sent to will figure it out to you. Maybe from mixers, casinos, etc.