I am not sure if I can sign a message with these addresses now. but why do I need to do that? my account is not hacked. I can still login into my account with my 3years old password. I don't think I need to sign a message in this case.
Signing a message is a way of proving ownership of your account. The forum's security system likely noticed suspicious activity (could be someone else who tried to login to your account using security question), so for that reason the account was locked. Now you have to prove you're the rightful owner for it to be turned over to you.
You didn't answer the question about getting an email address along with the notification. Locked accounts usually get one which they communicate with for recovery.
1: no there was not any suspicious activity as you are thinking. an admin can easily verify that. and I can't sign a message from those wallets. I don't have access to them.
2: yes there is an email with that not. and I've sent an email to that. the email looks very old tho. I don't know if it's still active or not. this is the email: