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