Here is the full list of all 19 Divide By Sheep achievements. It takes around 6-8 hours to unlock all of the achievements on Windows.
Get all stars in Ice World
Get all the achievements
Beat the 5th world with 3 stars in all levels
Get all achievements in 5th world
Beat the 5th world
Send a sheep through a portal
Use the totem to crush a critter
Get all stars in Spring World
Beat the Spring World
Get all stars in Dark World
Beat the Dark World
Burn the first sheep
Beat the Ice World
Put a wolf in a cage
Get all stars in Green World
Beat the Green World
First blood
Eat the first sheep
Drown the first sheep