Does anything exist for this 40-50 hr beast? :)

How does this run on Steam Deck?

Hey y'all, I've upgraded the skills with stars in em but i can't seem to use them. what might be the problem?

Like, can you just have ecchi with each and every girl as in true harem, or you should stick to one to avoid jealousy, route locks and/or something else of that kind? Also if it's former, why do they provide a choice in those events at all ?...

I guess my main questions are: Is there adjustable difficulty and is this pretty traditional turn based fare? :)