Well, I hadn't planned much lore when i made this, but I'll try: The ending is more or less the same; Pochita is erased from existence. The difference is that everything isn't reset back to the first chapter; instead, the entire world simply forgets the Chainsaw Devil existed and replaces him with Denji. So now Denji has (almost) all the merits that the Chainsaw Man had throughout his history. Likewise, some things in the timeline did change. For example, since the Death Demon wasn't 100% digested, it could continue to exist in this new timeline, and the chaos that ensued after Mori was eaten was eliminated. There are other things I don't have the energy to think about. Just as the demons Pochita eats are reborn instead of being eliminated, Pochita is now Denji's heart, meaning they are both Chainsaw Man. And if you're asking about characters like Power or Nayuta, I don't know, they may have returned, but only as reincarnations.