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