If Obito had never went on his mission with Kakashi kept both his sharingan

[Natsu Shazneel]

False, he would get blind the quickest. Because he wouldn't be able to spam kamui, the only reason he is able to spam kamui is because of Hashirama's cells, which gives a huge boost even better than EMS. Because hashirama's cells lets you regenerate instantly fatal wounds.

Obito would have died in the uchiha massacre and would never have made an appearance on Naruto manga. He is what he is only because of Madara(Giving obito Hashirama's cells meaning half of obito's body and brain that is).

Would Uchiha massacre still happen had the nine tails never attacked?

 

[loadsamoney]

but then kishimoto would have never made a plot of the obito as villian

 

[Tantalus Thief]

Would Uchiha massacre still happen had the nine tails never attacked?

The massacre was caused by the coup d'etat but the Kyuubi attack must have caused some distrust to the Uchiha.