Thanks again for the detailed review :)
The door on the second floor can be opened if you solve the riddle. There is a note with a hint on the first floor.
The notes can be read in the inventory. The madness scale can be reduced in the closet or with the help of sedatives.
The level is passable, the door under the stairs leads to the next level (there is a temporary ending of the demo version).
The demo version also has several secret rooms. You can get into them by solving riddles.
I deliberately do not give detailed instructions in the game so that the player can explore the world of the game himself. I do not lead him by the hand like in modern games. The riddles may not be very obvious like in old adventures.