Thanks I managed to 100% achievements the game finally :), I admit it didnt even cross my mind to do that.
Congrats! As far as I know you're the first to get there.
By the way, did you try clicking on the button below the achievement percentage once it's over 85%? Just checking if it does look like a button to people.
(Also the reward is a little half-assed, pun intended, but we'll try to expand this feature on the future.)