Alright, so you've answered this in two variations before, but with contradictory answers: Is Dirk's tiny Maplehoof actually the Maplehoof that came down with Bro2—and if so, how the hell did it get to the future, never mind the diminution—or is it a different horse?

It’s likely a different horse. That or Dirk’s Bro kept Maplehoof alive long enough for him to get his hands on some miniaturization tech and a sendificator