Here is the full list of all 19 Spooky Bonus achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Beat the game in Timed mode.
Beat the game in Relaxed mode.
Purchase all of the house decorations.
Purchase the Grey Alien decoration.
Reach the Crypt.
Set off a Garlic Bomb
Use all 6 powerups on a single level.
Upgrade a powerup to level 3.
Collect 10 coins on a single level.
Reach the Asylum level.
Reach the Dungeon level.
Score 8000 in a single level.
Find a black cat.
Score 5000 in a single level.
Set off 20 bonuses on a single level.
Collect a bag of coins.
Chain react 3 bonuses at once.
Chain react 6 bonuses at once.
Match 5 shapes at once.