Depends on their history. If they were together for a long time there might be friendship left.
i think that's not very common but i understand the situation and i believe if it feels right, go for it
That does not sound common to me in fact I do not know of anyone personally that got back together w/an ex after 2 yrs.
i do not personally know and i am sure others might but this should be something you decide upon not others do not let others control your fate and tell you what to do, do something your self be your own master rule your life with your self.