Here is the full list of all 39 Opus Castle achievements.
Final Office Room
See the pictures of the office
Interact with 3 verifiable items
Collect the Gun
Find pin 3 of the key
Collect 3 items
Go to the entrance
Interact with the mirror
Use your cell phone flashlight
Find the base key
Play with the goat
Take a look around on the town
Try to run
Get run over
Collect the cassette player
Access the company's app
Change the cell phone's wallpaper
Check up the stairs
Enter the suite
Enter Alvaro's bedroom
Enter the dinner room
Find pin 1 of the key
Find pin 2 of the key
Steal the jewels
Collect the pot of mugwort
Take a deep breath with the cigarette
Get a drink
Drink until fall
Collect the invocation tape
Eat a little
See the photo of the hall
See the photo of the suit
See the photo of Alvaro's bedroom
Open the drawers
Interact with 7 verifiable items
Final Suit
Ending Room of Álvaro
Ending Dinner room
Achieve all achievements