Does a Quilava with Flash Fire evolve into a Hisuian Typhlosion with Frisk?

Question

Assuming that it evolves into the hisuian variant.

Answer 1

Yes --- both Abilities are in the Hidden Ability slot, and there's no way to change that through evolution. Note that Hisuian Typhlosion only has Frisk starting in Scarlet and Violet; your Quilava will evolve into a Hisuian Typhlosion with Flash Fire in Legends: Arceus.