Here is the full list of all 25 Poi achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Beat the game in New Game+ mode.
Find all of the hidden costumes.
Collect ALL the Explorer Medallions.
Find ALL the Golden Gears.
Find ALL the Fossils.
Discover ALL the Locations.
Collect all the Explorer Medallions in Crystal Cavern.
Take a picture of ALL the creatures.
Find the legendary treasure.
Meet the requirements to open the Mysterious Gate.
Collect all the Explorer Medallions in Sinking Sands.
Rescue all the baby Pin Birds.
Collect all the Explorer Medallions in Mount Magma.
Visit the hidden planet.
Take a picture of the Master Explorer.
Collect 10 Explorer Medallions.
Collect all the Explorer Medallions in Cozy Canyon.
Find a hidden hat.
Do a triple jump.
Discover the mysterious travelling merchant.
Hey, watch where you're rolling!
Purchase an item from the shop.
Sometimes, things don't always go as planned.
Kick a Bucket Head.
Earn your first Explorer Medallion.