Here is the full list of all 18 God's Basement achievements. It takes around 3-4 hours to unlock all of the achievements on Windows.
Answer the phone.
Ignore the phone that constantly rings.
Solve the puzzle with the green cubes.
Watch the black box as it begins to move.
Get past the keypad puzzle.
Find Grandma's keys.
Hear three loud knocks next to the barricaded door.
Stack all 50 boxes.
Clean the two broken plates inside the house.
Read the old documents that reveals your past.
Hear the recording from the TV.
Find the security card.
Stand next to the rocking chair.
Let the Operator ask you a few questions.
Enter your old house.
Lay in bed while you hear a commotion outside.
Place the radio, the knife and the phone in the correct places.
Listen to the Operator's last monologue.