It's hard to say, we could assume that the rinnegan is formed with the sage's blood, some form of eyes and strong emotion. When the sharingan kids are born they have normal eyes, like Nagato had, so I think that he could have been implanted with pre-awakened sharingan eyes, then with the emotion used to awaken the sharingan his eyes became the rinnegan.
I think that Madara is who he says he is, he just has little power. Maybe he had most of his Chakra blocked, with a Hyuuga style technique. But the mask is simply a symbol, the best evil leaders travel with a symbol rather than a face, his face would have been mistrusted by even evil shinobi, so as Tobi he can travel the world without being bundled by ninja. Also it looks cool, and adds mystery.
I think that Madara is who he says he is, he just has little power. Maybe he had most of his Chakra blocked, with a Hyuuga style technique. But the mask is simply a symbol, the best evil leaders travel with a symbol rather than a face, his face would have been mistrusted by even evil shinobi, so as Tobi he can travel the world without being bundled by ninja. Also it looks cool, and adds mystery.
