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