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 unlocked all artworks.
Tarant showed you his Nyan Cat talent.
You beat the game and unlocked all the content.
You found all fireflies.
You helped the ghost to transmit a message.
You unlocked all the Musicom.
You died against the Blob.
You beat the game and saved Teddy.
You died against Tarant.
You helped the Spider Mother to get back it's lost baby.
You died against the second Spider.
You died against the Crocodile.
Mr Cat joined you.
You died against the Spider.
You found a firefly. Find them all !
You died against the Snake.
Mr Bug joined you.
You died against the Monster.
You died against the Wasp.