Most of the answers your looking for can be found in the “Chat Room FAQ” and “Epona Services” sections of the forums. I’ll try to nock a few off right now though:

1. Yes if you don’t register the room on the chat server with services. (chanserv)

2. Yes they can unless you make it so they cant.

3. What blue greeting?

4. Yes if your nickname and room are registered with services and you have identified for your nickname with nickserv.

5. Yes they can do it themselves.