A single app can have separate interfaces for mobile and desktop. Mobile/Touch interfaces are uncommon right now because linux on mobile isn’t ready, and it is extra work to make a separate GUI.

No, but it is going to take a considerable amount of time as they don’t have the manpower and resources of a multi billion dollar company.

You are buying a bicycle online.

Both are the same price, but one is handmade by a skilled professional with decades of experience, the other is made by a sketchy machine that even it’s creators don’t really understand… and sometimes uses square wheels instead of round.

Your choice.