Here is the full list of all 26 Lila's Tale and the Hidden Forest achievements.
Defeat the little Red Wing 100 times.
Defeat the big Red Wing 25 times.
Defeat the jetpack Red Wing 100 times.
Complete perfectly all stages.
Complete all stages.
Conclude a desert stage without falling into quicksand.
Conclude a volcano stage without falling into lava.
Finish a game stage without help from Flee or Zip.
Get a new outfit.
Find a secret passage.
Play an entire level with a friend.
Find all the owl eggs.
The first death by thorns.
The first death by fall.
Retrieve Flee or Zip at the last second.
Finish an entire level by defeating enemies with just the power of the Flee or Zip.
Defeat all stage enemies just by jumping on their heads.
Complete all stages with another player.
Lose the same bonus stage 5 times in a row.
Release all owls.
Take no damage while using the magic carpet.
Defeat the boss without taking any damage.
Finish a stage without defeating any enemies.
Complete all the bonus stages.
Find all hidden passages.
Lose a bonus stage by time out.