I think the idea is that Tenet and Cheney have Top Secret clearance, Libby and Rove do not? I am not sure.
I am certain that Libby and Rove have Top Secret clerances as well as other compartmental clearances above TS.
Yes, but then one has to assume that all were aware she was covert. If she wasn't, or if they were not told she was, I think all are free to talk about her to whomever they want.