It is not popular among educated people. You had better use "hanımefendi" but in spoken it is "hanfendi".
I would say no. I hear "abi" a lot used between younger guys to show respect to each other, but I (personally) have never heard "abla." I sometimes call my closer friends "abla" though :)
i think the answers should require stating exactly which relation exactly is referred to. (yani bu ablam örneğini kullanıyor) especially because it's point is to teach the relations.