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