There are eight Achievements you can achieve in this game. They can be achieved at any time, and through a number of conditions. However, it is worth noting that, after completing World 1-6 and getting the first Royal Sticker, there are eight Super Flags in the Sticker Fest area of Decalburg. You can examine them to check on your progress to the Achievements.

Achievement	How to unlock
Super Flag Achievement	Find every single HP-Up Heart.
Super Flag Achievement	Collect every sticker type in the world.
Super Flag Achievement	Make all of the secret doors appear.
Super Flag Achievement	Collect all of the Comet Pieces.
Super Flag Achievement	Spend 10,000 or more Coins at shops.
Super Flag Achievement	Get a Perfect Bonus (win without getting hit) in 500 or more battles.
Super Flag Achievement	Perform 1,000 or more "Excellent" Action Commands in battle.
Super Flag Achievement	Get three symbols matched on the Battle Spinner slots 50 times.