A lot of people limp PP. In hand one, he is representing a set, which is definately possible; Small bet to get value on the hand, then he reraises your raise the minimum amount. I might fold with no reads, your call though.

Hand two is interesting, all your moves fine, i just have no idea what this guy has!

hand three has a lot of possibilities. It could be a busted flush draw, or limped A7s. The thing is, he most likely doesn't have the straight. I might try a raise here, but thats only if i was really thinking clearly.