Just contacted live support again few minutes ago, luckily there is online support so I got fast responses.
Support has just confirmed by email manually so I can use the forgot password feature and I can login now but support ask me to complete KYC.
I'm not sure if it is mandatory or not, but support ask me to do it once I can login back to my account.
I used to play sherbet several times and made withdrawals several times and they didn't ask for KYC. However, after I was inactive for about 3 months I was asked for KYC, I did it and their KYC system was automatic, KYC would be approved automatically after we sent the data they needed. So far I don't think Sherbet has sent me any promotional messages either via email or anything else. I think it's safe for KYC here
If you use your account normally, all go smooth but if you are inactive a long time, login your account, it can trigger their systematic security alert and they can ask you to do some steps to verify ownership of the account.
Maybe what happened to me was because I had been inactive for several months so they asked for KYC