The numbers actually correlate to the boss’ attack pattern. As for how to get in, interact with one of the pillows in said rest area multiple times (I forget which one specifically). I’m sorry, I don’t fully remember the hint I gave for this
As for the last area, it’s the small side area that’s on a separate screen in like, the first floor of the second stratum? I forget which specifically, but it’s the one where you push a Rock Slime down some stairs to access. Just worry about this one last, because nothing changes until you beat that third boss.