Answer:
Turns us on our backs, and open up our stomachs. You will be the wisest of men though at start a lummox.
The eight of us move forth and back. To protect our king from the foes attack.
Of these things - I have two. One for me - and one for you. And when you ask about the price, I simply smile and nod twice.
I have an eye but cannot see, You'll head inside when you see me.
Although my cow is dead, I still beat her. What a racket she makes!
You use it between your head and your toes, the more it works the thinner it grows.
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?