Here is the full list of all 31 STAY achievements.
End Quinn's journey with a feeling of Depression
Collect all the other achievements
Reveal all possible endings
End Quinn's journey with a feeling of Denial
End Quinn's journey with a feeling of Isolation
Discover all possible items
Back to square one
End Quinn's journey with a feeling of Anger
Unveil all secret rooms
Stare at the full moonlight with Quinn
End Quinn's journey with a feeling of Bargaining
Reach the final chapter with the highest emotional bonding
Reach the final chapter with the highest level of trust
Become the perfect soulmate and never leave Quinn
Cracking the final code
End Quinn's journey with a feeling of Acceptance and Hope
Memories shaped into bits and pieces
Dance with the ugliest partner
Bad hair day not allowed
Play it cool
Don't lose sight of the north
Hail to the chief
Never leave the magic circle
Board game solitaire
A life within a life within a life within...
Guardians, feathers and the unknown
A never-ending book which is not for Bastian
Don't leave during a time interval
Never kill the cat
Who are you, stranger?
And then there was light...