There are a few rooms in the 1st Class Cabin and you will be required to travel to and fro them to get the items required. I will group the section by the steps you have to travel to in order to escape.
Full video walkthrough guide
Bedroom
Check the bed and under the pillow, you will find score plate (A).
Check the piano and you will find a map of the ship.
You will find 2 doors that you can open. Open the one on the right and you will a safe on top of a cabinet. Open the door to the cabinet and you will find score plate (C).
You won’t be able to access the safe until you have unlocked Safe Ending.
Living Room
Go through the door on the left and open the door in front of your. Skip the door to the bathroom as you won’t be able to do anything inside for now.
Grab the vase by the door as you will need it to fill with water.
Open the left door where you just grab the case. In the cabinet, you will find score plate (G).
Bathroom
Now head to the bathroom and fill the vase with water.
Then unplug the bathtub and you will find score plate (D) at the bottom of the tub.
Living Room
Now go back to the living and check out the fireplace. You see something inside but you can’t reach it due to the fire. Use the vase with water on the fireplace.
Reach for the item inside the fireplace and you will receive score plate.
Bedroom
Go back to the bedroom where the piano is and place the ceramic score plate and the glass plates on it.
Take note the Zero had screwed up the keys on the piano so you might need to trial and error a bit to get the correct score. A quick guide to the keys is below:
The lock on the door is now green, which means you have successfully escaped!
Sharbit Guide 