The limit existed on the 3DS as well, I don't really get it and I doubt I'll run into a problem with it, but it is nicer than having them expire, IMO.
As for the demo, the first level sucked, hard. I really hope there's not much of that kind of fare where you're escorting Murphy around.
Second level was pretty solid, the extremely BG&E music was fun to listen to as well, wish it lasted the whole level.
Third level was basically the mobile game but with more production value, it was good fun. I hope if there's more levels cut of this cloth it gets really challenging like it did on mobile. Having nothing to really collect and no grading present is a little troublesome, but it is just a demo.