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