Here is the full list of all 50 Merri Puzzle achievements.
Beat Expert Mode
Reach Expert Mode Check Point 6
Encounter Invisible Walls
Reach Expert Mode Check Point 5
Reach Expert Mode Check Point 4
Reach Expert Mode Check Point 2
Reach Expert Mode Check Point 3
Use Green Blocks To Break Red Blocks
Multiple Objects in One Room
Reach Expert Mode Check Point 1
Reach Expert Mode
Beat Hard Mode
Reach Hard Mode Check Point 3
Reach Hard Mode Check Point 2
Reach Hard Mode Check Point 1
Beat easy mode
Reach Check Point 14
Encounter yellow blocks
Reach Check Point 13
Reach Check Point 12
Reach Check Point 11
Reach Check Point 10
Break some breakable blocks
Reach Check Point 9
Encounter green diffuser blocks
Reach Check Point 8
Encounter exploding blocks
Reach Check Point 7
Reach Check Point 6
Encounter vanishing blocks
Reach Check Point 5
Use the red square of awesomeness
Reach a room with gravity controls
Reach Check Point 4
Reach a locked room
Encounter lava
Reach Check Point 3
Touch two triangles in puzzle mod
Encounter a peg based level
Use the wobbly triangle
Reach Check Point 2
MORE PITS!
This really is the pits!
Bounce things off of more things!
Encounter a level with two exits
Encounter a level with more than one solution
Check point found
Encounter a pit
Encounter gaps in a level
Make a ball