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 the legendary treasure.
Take a picture of ALL the creatures.
Meet the requirements to open the Mysterious Gate.
Discover ALL the Locations.
Find ALL the Fossils.
Collect all the Explorer Medallions in Crystal Cavern.
Collect all the Explorer Medallions in Sinking Sands.
Rescue all the baby Pin Birds.
Collect all the Explorer Medallions in Mount Magma.
Find a hidden hat.
Take a picture of the Master Explorer.
Hey, watch where you're rolling!
Collect all the Explorer Medallions in Cozy Canyon.
Collect 10 Explorer Medallions.
Kick a Bucket Head.
Do a triple jump.
Visit the hidden planet.
Discover the mysterious travelling merchant.
Purchase an item from the shop.
Sometimes, things don't always go as planned.
Earn your first Explorer Medallion.