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