You don't lock a thread, a moderator or a staff member from support can lock it. When a thread gets locked no more posts can be made on that thread.
I recommend you start replacing them with Tier three and it is entirely up to you on which ones you move in. Tier 3 cost 16m for level 1, 30m for level 2, 39m for level 3, and 45m for level 4. I personally have nurses and small town goddesses
You can't really delete the game; closest thing to deleting the account would be to reset the account-don't create a new username just reset-and delete the app. That should bring up Invalid User to whoever tries to follow any links from your account.
It means the person reset, either by their own free will, or because ATA has deleted the account due to prolonged inactivity.