When he said the Rinnegan's full power he's probably talking about both eyes since the page before he was told it might be some time before he gets the other eye
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That's not what he said or implied, especially when he just used the full power right there and then
We don't really see Madara absorb ninjutsus as he did as a Edo tensei. He summoned the Gedo Mezo but he did tell Obito he can summon and control it with just having Senju/Uchiha DNA. I don't know where Limbo or Rinbo came from but I think Kishi didn't give him S.T because it would be too strong for others to fight against. He would deflect anything 8th gate Guy has, same for Sasuke and Naruto since the 5 sec was for Deva path and not the true user of the Rinnegans like Nagato did as Edo.
at bolded:
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Limbo isn't a six path technique, it's like a signature unique to each original eye holder.
Sasuke has the shift and Madara has limbo, six path Justus are open to those with a rinnegan, black rod infused, or both.
Obito was the Juubi Jin, the Jin usually retain some of the bijuu's power in them, Gaara for example. I think being an ex Juubi jin had more to do with it than the Rinnegan then use the Rinnegan to pull out some chakra but I can be wrong.
Being a juubi jinchuuriki just allows you to take in senjustu chakra.
It allows you to pull out bijuu chakra if they let you.
Obito wasn't friends with the bijuu and chakra removal is another method to remove a bijuu.
Obito was even able to use it against kushina, but with that time he needed the seal to be weaken.