I just started playing after a long break; everyone on my friends list seems to have changed their name. How do I find out who they are (their original names)? Some of them have not come online yet, so I cannot ask them. If they have changed their name, then stopped playing, (now F2P) would their name have changed back?

If you hover your cursor over their name (assuming there is an icon which indicates a name change) you will be able to see their previous name. And no their names will not be changed back if they return to FTP.

I had this same problem. All my friends kept changing their usernames, got so confused that I had to delete everyone :(. Still only have 4 friends on my list. My advice though: give them nicknames, then you only need to ask for their nickname to know who is who...