Comparison of Obito and Tobi

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I know Tobi died alongside Kakashi and Rin in kakashi gaiden. I was just curious that why there is only one sharingan left with Tobi and it's on the left side of his? The same side of eye that was remained of Tobi before he died? Would it be possible that Madara is using Tobi's body to walk again as Obito? It really puzzles me so much...