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