1. A: I know that when you insert a Gameboy Advance cartridge, it stands out compared to the DS GB slot and also the Stylus is bigger and doesn't fit in the Orginal DS Stylus compartment, the buttons are more comfortable as well as the whole DS.
4. A: No, only the bottom screen can be used for touching.
Sorry, I don't know about the rest of the questions because I truly don't have the DS