Here is the full list of all 20 Dune Sea achievements.
Complete First Checkpoint
Make a Turn and Back
Airbourne for 50 meters
Land on a Platform
Passed the First Puzzle
Beat the First Chapter
Collect a flock bird
Glide for 50m
Bump into rocks 5 times
Scrape 5 rocks
Crash into ground 10 times
Fly back 100 meters
Collect 150 Seeds
Collect 20 Fruits
Collect 10 Gold Flowers
Pass 4 Checkpoints in a row
Roll + Honk after Puzzle Solve
Roll + 2 Honks after Dive
Dive Through a Cloud
Get 6 Flock Birds