Yes, members can have capture pages add contacts into a specific contact group. Also, they can transfer contacts betwen contact groups.
No, they are 2 separate things.
Setting up a contact group allows you to group your contacts by specific criteria. IE: active contacts, inactive contacts, etc. You can assign each contact group specific autoresponders, and even specific capture pages.
Trackings are created to track where contacts came from IE: facebook, or a specific capture page.
To protect contacts that have requested to have the account inactive there is no way to reactivate them. The only way is for the contact to reactivate themselves by either using their password or by using an IP that they previously used. The other option is we can reactivate them for you through the database.