Here is the full list of all 14 Conway: Disappearance at Dahlia View achievements.
Unlocked all secondary observations
Completed all character bios
Uncovered someone's true identity
Located all stamps in Dahlia View
Solved all evidence review scenes without making a mistake
Solve Downes evidence review without making any mistakes
Caught the objects first time in Doerr Manor basement & in The Crow's Nest
Got a perfect score when playing darts
Unlocked the shoe observation in every observation scene
Solved Doerr's evidence review without making any mistakes
Restored the Doerr Family Portrait
Solved Levy's evidence review without making any mistakes
Dropped the box off the shelf in Levy's Garage
Solved McKee's evidence review without making any mistakes