When claiming victory in 011, can one select a character other than the Chosen One or Fenrir?
I think no, in both cases.
The rulebook (PDF) specifically mentions that when declaring victory, and as quoted by you (emphasis mine):

If you are a hero [...] you must move the Chosen One (by the normal movement methods) to the building where the Organ of Eternity is located
If you are the incarnation of Fenrir [...] you must move the character whose card you have in your hand (by the normal movement methods) to the same space as the Chosen One

I think &quot;you must move the character whose card you have in your hand&quot; rules out a Fenrir victory by bringing the Chosen One to him instead of selecting and moving Fenrir to the Chosen One.
In your second scenario, both cases in the rules specify &quot;by the normal movement methods&quot; which I think precludes moving a different character to the objective and then using a special movement technique to swap two players' locations.
The clarification allowing players that are declaring victory to select any character is presumably just a way to avoid meta-gaming and players choosing specific characters only to prevent an opposition win (or heroes accidentally working themselves into a corner).