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 found all fireflies.
You unlocked all artworks.
You died against the Crocodile.
You died against Tarant.
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 helped the Spider Mother to get back it's lost baby.
You found a firefly. Find them all !
You died against the second Spider.
Mr Cat joined you.
You died against the Spider.
You died against the Snake.
Mr Bug joined you.
You died against the Wasp.
You died against the Monster.
You died against the Blob.