Here is the full list of all 33 The Gateway Trilogy achievements.
Open the remote controlled door
Listen to a comment
Arrange the pearls in the most obvious way
Enter numbers you shouldn’t know
Complete Gateway I
Find the first video tape
Find the second video tape
Find the third video tape
Find the fourth video tape
Don’t electrocute the pupil
Don’t poke the eyes
Transfer all the video tapes
Complete Gateway II
Feed The Sleeper, a lot
Upset the stomach
Activate the limbs
Activate the lungs
Complete the bowels
Spawn a copy
Complete the spine
Free The Sleeper
Don’t trigger a single step plate error
Complete Gateway III on normal difficulty
Find the secret ending
Activate the circulatory system
Exact The Sleeper's revenge
Spare the shift worker
Play Funkytown
Electrocute the pupil, a lot
Complete Gateway III on hard difficulty
Enter The Sleeper
Offer a gift to the shift worker