Private Threads and Avatars?

[mera]

I'm working on our new forum and have LOVED the tutorials. A couple questions though that I can't find answers too. But first, our temporary website is http://merakohblog.com/phpBB2/.

1. I want to have certain forums be private to select people. Is there a way to create a password that can be emailed to these people so they have access to the private forum?

2. What do I need to do so people can upload their own avatars?

3. How do I require everyone to register before they can start posting, just like I did with yours?

4. What's the difference between a Usergroup and creating a forum for a private group?

Thanks so much!
Me Ra