1. can i delete old versions of a page? how do i do this? copy the page?
Not over the web user interface. However you can setup a cron job to delete all old revisions older than a period. Search the Splitbrain Wiki to find instructions on this.
2. can i change the group to which a user belong? I dont have an option to edit any of my users.
Take a look at the user manager in the admin menu.
3. can threads be expanded/ collapse with the discussion plugin? any links on how to do this?
I guess it's not currently possible. Can you elaborate on what you want to be able to do? Then submit a feature request at
the issue tracker of the Discussion Plugin.