Here is the full list of all 20 Meld achievements.
Create a single stack with 20+ elements.
Buy a powerup from the store.
Complete level 50.
Complete level 100.
Complete level 200.
Earn all 600 stars.
Progress to rank 20.
Create a conduit with 30+ elements.
Destroy 10+ elements with a single pulsar.
Create a conduit with 4+ colors.
Finish level 15 using only two antimatter powersups.
Finish level 47 with exactly 10 moves left..
Finish level 48 using both Super Conductors.
Finish level 80 with no purple elements on the board.
Finish level 92 with only yellow elements on the board.
Finish level 101 with exactly 1 move left.
Finish level 139 with only purple elements on the board.
Finish level 141 in under 45 seconds.
Collect all plasma on level 152.
Finish level 171 in under 22 seconds.