Here is the full list of all 14 Journey On Playtest achievements.
Obtain an Adventurer's Permit
Defeat a Mimic
Defeat Abomination of Agony
Meet father in dream
Fish up an equipment
Obtain all 5 Legendary Weapons
Learn the Ultimate Spell of Destruction
Complete the game once
Obtain the best ending with less than 2500 Darkness Affinity.
Learn all the techniques from Training Books and NPC.
Enter the Abyss.
Help a cat and a dog.
Obtain the Serpent Scale Armor
Sucessfully convince the Corrupted Assassin to leave without a fight.