Here is the full list of all 20 The Guest achievements.
Get to the end.
Collect all possible objects.
Type the password in the computer.
Complete the dream maze scene withouth failing.
Listen to some music on the record player.
Read all the newspapers.
Turn off all the lights.
Complete the music puzzle without failing.
Use the sign and don't be disturbed.
Try lighting a cigarette.
Enter the toolbox password without combining the notes.
Wait 8 hours and hit the button again.
Get into the secret room.
Complete the valves puzzle in less than 20 movements.
Try consuming the bath pills again.
Call every single number on the phonebook.
Write BENEFACTOR on the typing machine.
Locate the Team Gotham's headquarter.
Be thankful twice.
Solve the batteries puzzle in just 2 movements.