They are all centralized exchanges, they can ask for KYC at anytime.
I use Huobi global and OKX among all.
I was unable to access Huobi global derivative trading until I did KYC. Maybe this has changed
On OKX, I was able to use derivative trading, and able to withdraw to certain amount. I left the exchange for like a month or two. When I went back to the exchange, I deposited some amount of bitcoin. I converted it to USDT. A time came when I wanted to move the USDT to another address, i was asked to verify my mobile number. I was unable to withdraw until I verified my mobile number. I wanted to create a thread about this some months ago when it happened, but I just thought it is not necessary because it is still a centralized exchange.
People should know that using centralized exchanges can come with some inconveniences too like freezing of your coins and blocking of your account. But even if this is not the main discussion of today, there is still the fact that they can freeze your account and demand for KYC compulsorily.
Agree with what you said friend, because of my experience before last year I had an account with binance, it has 2FA, and I am also fully verified on their platform. The time came when I opened my account in binance, I couldn't enter because when I entered the 2FA code it was always invalid, and I chatted with their support and that's exactly what happened.
Then, I was given instructions and I followed them, but in the instruction that was given, I needed a 2FA code, it's always invalid, so I said maybe I can unbind my 2FA and I was told that it's not possible, now I showed my transactions in binance like deposit and withdrawal and that's uid number b, as well as my full name and mobile number, then they gave it to me and what they did was pass me KYC again and then my 2FA was unbinding and I changed it to Authy not google authenticator.
It just means that the centralized exchanges can freeze the account, they can also bind our 2FA.