Here is the full list of all 19 Finding Teddy achievements. It takes around 2-3 hours to unlock all of the achievements on Windows.
You died against the Monster.
You died against the Wasp.
You beat the game and saved Teddy.
Tarant showed you his Nyan Cat talent.
You found a firefly. Find them all !
You found all fireflies.
You unlocked all artworks.
Mr Cat joined you.
Mr Bug joined you.
You died against the Blob.
You died against the Spider.
You died against the Crocodile.
You died against the Snake.
You died against the second Spider.
You died against Tarant.
You unlocked all the Musicom.
You helped the ghost to transmit a message.
You helped the Spider Mother to get back it's lost baby.
You beat the game and unlocked all the content.