I just 100% the game, aside from max leveling each character. Key to rewards drops at floor 7+. Once you get one, you can go back to the previous floors and unlock those doors. You’ll need to re-input your cards as it doesn’t save them
I cannot wait to get off work and play it. I've been doing a new run of the original this week finished the child section yesterday so I guess that's decent enough before remake. I'll probably go back and finish the original playthrough but remake is going to take precedent for a while