I’m gonna say Jet Force Gemini. It’s not hard in that enemies or bosses are difficult, though some were. It was those damn Tribals. You had to save every single one of them if you wanted to beat the game, and some were a pain to save without them getting killed.
I’ve always read hardware to mean the console itself and software to mean the games when it comes to consoles. So I would expect the games to be playable whether they are digital or physical games. I’ve seen nothing to suggest Nintendo want to go the digital only route anytime soon.