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