Full list of all 30 Tell Me Why achievements worth 1,500 gamerscore. It takes around 2-3 hours to unlock all of the achievements in the base game on Xbox One.
The base game contains 10 achievements worth 500 Gamerscore, and there are 2 DLC packs containing 20 achievements worth 1,000 Gamerscore.
Completed Episode One
Remembered the night the twins agreed to lie
Entered the Ronan House
Found your first Book of Goblins figure
Left Fireweed Residential Center
Make Tessa tell everything she knows
Find the password to unlock the Police Station computer
Solve the puzzle on Mary-Ann's door
Take time to talk things over with your twin
When we say locked, it's locked
Completed Episode Two
Made peace with Mary-Ann at the cemetery
Won the plushie battle
Discovered intel about Mary-Ann's past and her death
Found a recording of the twins' 911 call
Corrected the old graffiti on the tree
Figured out who inspired each Book of Goblin character
Stick a note on Tyler's back
Prove to Tyler that moo boxes are actually funny
Find three classic posters
Completed the story with the twins strongly bound together
Locked-up and left the Ronan house with Tyler
Uncovered the princess' lost treasure
Caught all the fish with Michael
Learned the truth about Sam's relationship to the twins
Start writing a new chapter with Alyson
Complete the story with the twin's bond weakened
Place all collectibles in the attic
Help Sam fix the engine
Find out who the Mailbox Bandit really is