a) How did Hiro and Ando know about Claire? In the beginning of last week's episode Hiro mentioned something about "we have to save the cheerleader!" before they stopped at the road-side deli.
Peter briefly talked with Hiro and Ando on the phone about Peter's encounter with future Hiro and his message.
I don't know about the second one, though I'm sure there was some kind of eluded explanation somewhere that I've forgotten.