I heard that MEXC exchange started introducing kyc recently, or there was some other issue with them.
On MEXC, after unverified is primary KYC.
I took this from my MEXC account when I clicked on verify:

But the 24 hours withdrawal limit that I saw is 10 BTC. This makes me think if I have done any KYC on the exchange but all I remember is that I did not do KYC on the exchange. And you can see that I have not done basic verification which is next after unverified.
But as you know, they are centralized. They can force any of their customers to get verified at anytime.
I do not use the exchange often, so make further research to know if the exchange is worth using.