Naruto Thread (Spoilers For Sure)

I don't think he can go back and forth between normal eyes and sharingan eyes, and then further to Rinnegan eyes similar to how Kakashi's Sharingan is active 24/7 and he has to cover it to not use it. Most likely because both of those eyes aren't his, they're taken from the person as to how it died.

Makes sense. Obito died with Sharingan, it stayed as Sharingan. Madara got Rinnegan right before his death. Tobi steals it and gives it to Nagato, then takes it back and uses one of them for himself, and since Madara is an Edo Tensei he gains the Rinnegan anyway like how Itachi and Pain have their eyes although in the real world they are stolen.