The ninja world is reborn, and everyone is resurrected at the start.

If everyone in Naruto went back to before the Third Shinobi World War, if Obito Uchiha went back to before he met Madara Uchiha, could he change his fate? If the Fourth Hokage and his wife were still alive, could Naruto's fate be changed?
If the Kage were to be resurrected ahead of schedule, would peace among ninjas arrive sooner? If Yahiko were still alive, would Jiraiya have been spared from death? If Obito had not started the Fourth Shinobi World War, would Neji have been spared from death?
If everyone is reborn, will regrets disappear? If those who died didn't die, will the era of ninjas never end?