You can find the "blood pack" in the storage on the 3rd floor in the "alternate" world.
If you use this blood pack in front of the Bloodsucker in room 204 on the 2nd floor, you can distract its attention from it, so you can approach the wall.

Obtain the "lighter" in room 201 on the 2nd floor,
and the "disinfectant alcohol" from the ICU on the 2nd floor.
If you first use the "disinfectant alcohol" and then the "lighter", the ivy which is entangled on the lattice door, will burn down.

The lattice door at the end of the dark passage, which is the equivalent of B2, is locked, but along the way in the dark passage, there is an iron door, from which you can enter.
You can obtain the examination room key in the hidden patients room.

Go north on the street where the shopping mall exists, which is located on the north end of the map, then you will run into the destroyed area, check the right side of the street.
You should see the sign saying "Green Lion". The entrance is in the basement.
Or, you can find the street address at the public phone when you leave the hospital.

There is a gun shop on the same floor as the one you fight Twinfeeler, in the "alternate" shopping mall. You will see the rifle on the floor in front of the broken show window.