Not tested myself.
Here is what I think.
1) Giving a negative trust
I think it is not possible to do that.
2) Changing their avatar
Possible. Allowed.
3) Changing their personal details
Possible. Allowed.
4) Trying to PM someone.
Ban evasion.
5) Changing your signature
Possible. Allowed.
6) Editing/Deleting your posts
Ban evasion
7) Watching/ Unwatching thread
No idea.
Creating a new account(but not posting) (Q. why is 8 Cool?)
Possible. Allowed. no posting, no PM. Why would someone do that, lol?
9) Using another account from a different IP, while its not known if the banned account is connected to the new account.
Death sentence if caught.
10) Posting in meta thread with a signature, about something which is not related to your ban
Ban evasion.
11) Trolling(only once) in meta thread
About his ban? Possible, Allowed or ban extension depends on the case.
Not about his ban in a different thread. Ban evasion.
Nothing above has been confirmed by me. Not reliable.
Disclaimer: If you were banned and you did something above listed as permissible, and got yourself perma banned, I am not responsible.