Here is the full list of all 20 Fallen Demo achievements.
Starting the game off with a bang!
Finding Dusty's Chronicles 1
Finding Dusty's Chronicles 2
Finding Dusty's Chronicles 3
Finding Dusty's Chronicles 4
Unlocking Hunter's Special Scene
Choosing the Hard Drink
Choosing the Light Drink
Choosing to drink nothing.
Accumulating All of Dusty's Chronicles
Survive the battle without getting killed the first time
Arriving to the ceremony in a fresh change of clothes the first time
Annoying Xa, the Chief
Winning at Arm Wrestling
Losing at Arm Wrestling
Dying in battle against Ajax
Unlocking all Parallel Scenes
Finishing the game
Asking the Chief everything that is needed to know
Scoring 50 points or more at Arm Wrestling