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