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