Sorry for the delay; I had a busy week this week!
21. - Do they share any interests or hobbies?
Oh absolutely! I see them both loving swordsmanship and horseback riding, even in modern day. (And they are very good at both. I see other characters sitting to watch if they decided to spar, or race.)
I also see them both knowing how to play a musical instrument. For Feliks, I headcanon that he's good at playing the piano (Lol, as a reference to Chopin), while I see Toris preferring to play a stringed instrument, maybe an acoustic guitar.
I also headcanon them both still being somewhat religious (despite everything they went through), especially Feliks, so, occasionally, I see them both slipping into the back of a service in whatever country they're in, if it's a Sunday. It makes them feel nostalgic, if that makes sense. (Though they joke around afterwards that they're still used to mass being said in Latin)
I also see them being into a lot of different hobbies and interests separately. For Toris, I headcanon that he likes to read and draw, as well as gardening. He's also more athletic than he seems at first glance; I see him being into basketball, both watching it and playing it. It's canon that he knows some form of martial arts, so I just headcanoned that it's specifically karate that he learned.
As for Feliks, it is canon now that he's into playing video games. But besides that, I see him loving shopping (specifically for clothes). I also see him liking to design clothes, so he has tons of patterns and sewing supplies in his house. I also see him being into cooking, as well as knitting.
And not that this really has anything to do with this ask, but I also see them having different love languages. For Toris, it's acts of service, and for Feliks, it's words of affirmation. (Which does sort of relate to the hobbies, like Toris loves it when Feliks helps him garden. Meanwhile Feliks loves it when Toris watches him game and comments on how well he's doing, especially if the level is difficult.)
Oops, that got so long! Thanks so much for the ask! :D