Almost you need to pass KYC to use centralized exchanges and it is the only way if you want to trade your cryptos for fiat and vice versa.For trading cryptos there are decentralized exchanges where the trading volume is really low compared to the centralized exchanges and also fee could be a lot.
So if you want to be a trader then you should be ready to do KYC at any time.And the reason for freezing accounts on exchanges are like receiving funds from blacklisted addresses, or what they doubt you involved in any shady activity or money laundering.
yeah right , you need to always prepare and ready to make aKYC in case you emergency need it there are centralised exchange that you can use even without a KYC but there are daily withdrawal limit . Example of that exchange is binance and kucoin you can use that exchange without a problem if its only for small funds .
They offer withdrawal limits but we can't be 100% sure they will never ask our any personal details, if government made strict regulations they can change their verification system at any time like what happened in Localbitcoins.com last year and in case of any suspicious activity they might lock your account and ask you to prove that you are the real owner of that account.