Here is the full list of all 16 Ophidian achievements.
Eat 100 food blocks total.
Eat 573 food blocks in one play mode session.
Use portal blocks 100 times total.
Use bounce blocks 100 times total.
Use bomb blocks 100 times total.
Complete 10 Challenge Levels total.
Complete 20 challenge levels total.
Complete 30 challenge levels total.
Complete 40 challenge levels total.
Complete 50 challenge levels total.
Complete 60 challenge levels total.
Complete 70 challenge levels total.
Complete 80 challenge levels total.
Complete 90 challenge levels total.
Complete 100 challenge levels total.
Classic Mode Unlocked