Here is the full list of all 20 The MISSING: JJ Macfield and the Island of Memories achievements.
Read all of the texts from the past.
First, you need to find Emily.
Select Continue after the ending and start a new run.
Jump over that black thing!
Read all of F.K.'s hidden texts after finishing the game.
Acquire every donut.
Don't get too addicted to your phone.
Read a hidden text from F.K. after finishing the game.
Complete the game.
Reach the top of the clock tower.
Escape danger.
Find every Sleepy.
Fall off a bridge.
Get run over by a train.
Crane operation is dangerous work.
Escape from something scary.
Find the first Sleepy.
Chat with F.K. for the first time.
Let the strange deer empower you.
Awaken at the campground.