Did ever plan to return to the world of Celeste?

Not really! The story we told with the original game was always a self-contained thing. It's a very literal journey for Madeline and her struggles, and the story, as it resolves in Chapter 7, is a complete arc from start to finish, with Chapter 8 as a bit of an epilogue. There were rumblings when we released the game that it'd be neat to do some super mega challenging levels as DLC, but certainly nothing to the extent that Chapter 9 became.

Did you have any fears/reservations about creating the soundtrack for Celeste: Farewell?

Plenty of fears, yeah. They were mostly about living up to expectations after the huge reception we received for the original release. I hadn't really sat down to write anything new until after we had been at a number of awards ceremonies, and it was such an exhausting and climactic series of feelings that I wasn't sure how I could even approach anything new.