Here is the full list of all 12 Eraser & Builder achievements.
Started the game.
Completely cleared the stage of 1st chapter.
Completely cleared the stage of 2nd chapter.
Completely cleared the stage of 3rd chapter.
Completely cleared the stage of 4th chapter.
Started the stage editor.
Create a stage by stage editor.
Upload a created stage to steam workshop.
Played the stage that I downloaded from the steam workshop.
Collected 50 feathers.
Collected 100 feathers.
Collected all feathers.