I try to answer 1:
First, I don't think there is a GUI-way of doing this since the unarchive code isn't implemented as far as I know, but if you follow this thread: https://openacs.org/forums/message-view?message_id=107445 you should find some code that you could use. But please use it on your own risk though - it's my own implementation and there can be things i've missed - with that said it looks like it works very well :)
It should be easy to provide a link in the Action part on the page for the archived communities.
Regarding "Cloning of classes", it's normaly only SWAs that can do that and you should find a link called "Copy this group" in the controlpanel of the perticular community you want to clone.