Here is the full list of all 20 Hour of the Snake achievements.
Complete any level
Learn how to play
Collide with a wall
Play for an hour
Pass the distance of 42,195 squares
Pass the distance of 875,000 squares
Reach a speed of 60 squares per second
Max out every length increasing level
Max out every distance passing level
Max out every survival level
Max out every fruit eating level
Max out every speed reaching level
Max out every star collecting level
Max out every painting level
Complete the campaign
Obtain all campaign stars
Change the appearance of the snake
Use a cheat
Hear the scream
Run the game during the hour of the snake