Board Thread:General Discussion/@comment-28378595-20160504145402/@comment-27701762-20160505015633

So if you're not facing Undyne the Undying, then the likely cause is that you actually aren't on the Genocide route, as previous actions should not be preventing you from taking a different path. The only time when completing any version of the Neutral ending impacts the rest of the game is through the True Pacifist route.

Meanwhile, the naming thing is standard. You can only rename the fallen human following a True Reset, which means you have to complete a True Pacifist or Genocide run. If you perform a normal reset, you are locked in with the name you already typed in.