1) Can dragons attack WHILE you are in a walled city? I have yet to encounter one inside a city.

2) Do unscripted dragons ever attack towns when i am not there? Like if i was in Whiterun, can a dragon still attack a town way in Rorikstead?

I've had dragons attack me in Solitude. I think dragons generally attack places near you. I think the dragons may hunt the dragon born for some reason

1) Yes, I have had a dragon attack while being inside the walls of Solitude.

2) I have yet to witness this so I am not sure. However, this could totoally wipe out NPC populations in villages so I would hope not.