ok so let me start from the start when madara vs the first hokage before he died like minato (4th hokage) put a little of himself into naruto. he put the most he could into a body and gave it one of hes ems (maybe a white zetsu clone like in other thread) then he escaped and then planing and...
Sorry to say but the rasengan in he's demon cloak state is the tailed beats bomb or thats how killer bee said it happens you can look it up he says rasengan is the Same kinda way the beast bomb works
Int theory on why he's cloak is different is because he didn't get the hole kyuubi in him only he's charkara and soul well that's what the toads told him anyway
I think he's not madara I know it's a long shoot but apart from having an old face why else and maybe kabuto always calls him Tobi because he knows he's not madara but doesnt know who he really is.