Here is the full list of all 17 HIDDEN CATS: The last of cats achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
Find the first cat
Find 5 cats
Find 10 cats
Find 25 cats
Find 50 cats
Find all the cats
Congratulate the pony on his birthday!
Find all the cats in the room
Find the cat in the bag
Find all the cats in the bookstore
Find all the cats on the roof
Find all the cats near the tree
Find all the cats near the car
Find all the cats at the party
Find the cat in the ad
Find the cat statue
You have passed the game