2017 Year,
China banned fiat currency trading virtual currency，
BTC ->CNY and CNY -> BTC, Illegal trading on the exchange.
However, user A and user B can seek guarantee from the exchange, and user A transfers money to user B.

CNY(UserA) -> USDT(UserB)，USDT(UserB) Exchange Buy BTC, ETH,....,  OK
BTC(UserB) Exchange Buy USDT,  USDT(UserB) -> CNY(UserA)   OK


2021 Year,
It is illegal for the exchange to provide services to the Chinese！
There is a high probability that there is no way to bypass

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Translated by google, I don’t know if I can express it clearly