just to add on to what sushimon said, i find the easiest way to get all 4 endings is to have four different save files and work that way. remember that level 2+ items will probably not be the first thing you find per dream!!
i really hope you enjoy the game, ending 4 makes all the hard work getting those layer 4 items worth it!
(also, W.T. has made a cameo in the fangame Me which is also on this wiki!)