Contained here within is a full walkthrough detailing how to get 100% in one playthrough.
Parts of this guide are from reddit users, thank you to the original posters.
If this guide helped you let me know.
Walk left through the cemetery and read all of the headstones.
Go left and enter the cabin. Turn on the light switch, then go to the far right and pick up the lighter from the kitchen counter. Return to the fireplace and use the lighter Achievement Light it up!
Examine the caged window and the TV, then go through the door on the far left. Continue through the hole in the wall of the bathroom, then through the door to the right of the couch.
There are 3 doors in the next hallway. Go through the one on the far right to see the numbers 8 and 1 flashing on a green TV screen. Return to the hallway and go through the one in the middle to see the number 18 written on the wall (this becomes invisible if you turn on the lights). Return to the hallway again and go through the door on the left. Examine the bloody washing machine and enter the code “1881”, then take the key that is revealed.
Head all the way back to the front room of the cabin and use the key on the locked door to the right of the bookcase. Examine the blood on the floor, then go back through the door.
Go right and talk to your wife, then the power will go out. Head out through the door on the far left. Go over and talk to the men on the left, then head downstairs twice to reach the basement. Go over and flip the second lever to turn the power back on.
Head through the door on the left, then continue left and use the elevator to get to the 3rd floor. Go right and through another door. Walk towards the sofa to meet 3 strange characters Achievement First Encounter
Leave the room again to see the layout of the hotel has changed, and you can now see that you were in room 300. Go right and into the WC, then head to the far right (the lights will turn off) and collect an angel statue. Go back out to the hallway. Enter room 301 and read the note here, then leave again. Search room 302, but all you will find is some boring documents.
Continue right and enter room 303. Walk to the right and pick up the sword shard from the body, then go back to the left (which is much longer than before) and leave this room. Go right and enter room 304, where you will find a cabinet that is stuck and cannot be opened.
Head all the way back past the elevator and into room 305. Pick up the crowbar from the sofa on the right. Go back out and try the next door, to find that room 306 is locked. Enter room 307 and walk backwards and forward to see that the door disappears, but it will eventually come back so you can leave again. Search room 308, but there is nothing much here.
Go all the way back to the right and into room 304 again. Use the crowbar on the stuck cabinet, then pick up the key. Go out to the hallway and use this key on the door to room 306. Go inside and pick up the holy book on the right. Go back out to the hallway and enter the unmarked door to the left. Use your sword shard on the knight statue, your holy book on the lectern, and your angel statue on the column. After a quick conversation, go through the door.
Head upstairs and talk to the man at reception, then go upstairs once more. Enter your apartment through the first door on the right and find a note in the bedroom. Leave the room again.
You are now on the second floor. Go right and enter room 201. Pick up the rope from the sofa, then leave. Continue right and enter room 202. Read the note on the arm of the sofa, then continue right to find some locked lockers, and pick up a purple record from the far right. Leave this room, then go right again and enter room 203. Try using the purple record on the gramophone, but it isn’t the right one. Go out, and then enter room 204.
After talking to the man at reception, go up one flight of stairs and into your apartment on the right. Walk over to the right and talk to your wife.
Continue right within room 204 and pick up the red record, then exit the room. Go left to room 200 and pick up an orange record. Look at the blank parchment on the right, then leave the room again. Go left and enter room 205, picking up the brown record before leaving. Try entering room 206, but it is locked. Go into room 207, but there is nothing of note here so leave again. Enter room 208 and pick up a blue record, then leave.
Go back to room 203 and use all of your remaining records on the gramophone Achievement The Record Listener
Then pick up the key. Go out to the hallway and use this key on the door to room 206. Go inside and pick up a lever, then leave again. Go to the far right and enter another room labeled 205. Use your rope and lever on the mechanism here. After another quick conversation pop goes Achievement Lovely Encounter
Go through the door.
Go left and you will be told the boss wants to see you. Continue to the far left and through another door. Go left to talk to your boss, then leave his office again. Go right and sit down in the empty cubicle.
Go right and enter room 100. Pick up the piano key on the right, then leave again. There is an unlabeled door that won’t open, followed by room 101. Enter here to find an empty cell, then leave again. Room 102 has nothing of use, so continue to room 103 and read the note. Pick up another piano key here before leaving. Room 104 also has nothing of use, so enter room 105 and take another piano key.
Return all the way to the left past the elevator. Enter room 106 and read the note here, then leave again. Enter room 107.
Leave the room through the door on the left. Leave your apartment and talk to the people at the staircase.
Continue searching room 107 to find a piano key, then leave the room. Go left some more; room 108 has nothing of interest, so enter room 109. Look at the note here to see the order of keys you will need to press on the piano. Use all 4 of your keys on the piano, then use the piano and play the correct sequence of keys. Go left and try the door, but it is now locked. Go right. After a short conversation, go through the door.
Go right to talk to the nurse, then head through the 3rd door on the right. Talk to the doctor, then go behind the curtains and pick up your baby Achievement The Baby
Examine the baby.
Read the note on the desk, then head through the first door on the right. See the number 7 written in blood on the mirror, then pick up the mannequin’s left arm. Leave here and enter the next room on the right. Pick up the mannequin’s torso before leaving again. Enter the third room to see the number 9. Pick up the mannequin’s left leg and leave again. Enter the final room to the right to see the number 2 and find the mannequin’s right arm. Go back out to the hall and head left past the desk and past the open doorway. Enter the first room to the left to find a safe requiring a combination. Leave for now and go to the next room to find the number 3 and the mannequin’s head. Go to the next room on the left and pick up the mannequin’s right leg.
Return to the room with the safe and enter the combination 9723 the correct order of the digits can be known by listening to the machine to the right. Pick up the key before leaving the room. Go right and through the open doorway into an office. Use your key to unlock the door in here and go through.
Walk right past the cells until the lights go out.
Walk right past the cells again and go through the first door Achievement Armless One
Go back out and enter the next doorway. Put all of your mannequin parts on the stand Achievement The Mannequin
Head right and use the elevator, then go left and through the large doors and head left to meet the president Achievement The Boss
Walk left through the cemetery and read all of the headstones.
Exit to desktop