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