Here is the full list of all 14 Doodle Kingdom achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Level up your Hero to level 21
Complete 3 quests
Create all elements in Main Game
Invent all spells
Create all magical creatures.
Open all elemental elements
Create all 3 towns
Buy 10 belongings for your Hero.
Complete 1 quest
Level up your Hero to level 16
Buy some equipment for your Hero
Level up your Hero to level 1
Level up your Hero to level 4
Level up your Hero to level 10