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