Here is the full list of all 16 In Between achievements. It takes around 6-8 hours to unlock all of the achievements on Windows.
Complete Denial
Die 100 times
Do a successful gravityzone jump
Complete Tutorial
Reach one MindImage
Complete all levels
Complete Anger
Complete Bargaining
Complete Depression
Complete Acceptance
Complete the game without dying
Reach all MindImages
Watch the credits
Complete five acceptance loops
There's more than one route to follow.
Find the 5 hidden glimmers of hope.