Hey Nikita,
1. Yes, there is a setting that will allow only registered users to post comments.
2. There is an option to accept comment, but don't make them public until a moderatator has approved them.
3. You can select a moderator group
4. It is possible to publish/unpublish & delete from the frontend for moderators
5. There is a plugin that will post the comments to the jomsocial stream (but it is not a module that sits on the jomsocial wall of the user -> the comments are shown in the stream)
6. There is a module to show the recent comment, most commented articles, best voted comments, but there is nothing for top commenter.
7. No, it currently doesn't integrate with alpa user points.
Regards,
Daniel