Here is the full list of all 13 LEGO Builder's Journey achievements. It takes around 2-3 hours to unlock all of the achievements on Windows.
Cleared the puzzles
Played with your new friend
Went on an adventure
Completed the hike
Learned to climb
Learned the basics
Found a way in the dark
Made your way through the danger
Went back home
Made your way up from the depth
Broke free from the machine
Imagined a way out of the dark
Journey complete