BuddyPress.org

1. I think there’s a restrict group plugin. Try a search here: https://buddypress.org/extend/ and you should find it.
2. This is the default behavior for groups/forums
3. The BP Album + plugin is working on this, but still not done. There’s another paid plugin out there that does this. Here’s a post I did on my blog lamenting the paid option versus the not quite ready open source option: http://www.crashutah.com/blog/juanchito/2010/05/26/buddypress-group-photo-gallery-plugin-thoughts/