Here is the full list of all 26 Arlo Playtest achievements.
Launch a game in play test
Buy an equipment
Buy all weapons
Buy all shields
Buy all helmets
Buy all armors
Buy all runes
Reach level 10
Reach level 20
Reach level 30
Reach level 40
Reach level 50
Reach level 60
Reach level 70
Reach level 80
Reach level 90
Reach level 100
Keep a level 1 skeleton alive till the end
Defeat elite level 1
Defeat elite level 2
Defeat elite level 3
Defeat elite level 4
Defeat elite level 5
Defeat elite level 6
Defeat elites level 7
Defeat elites level 8