Answer:
I am a desire to munch
I cannot be burned in fire or drowned in water
Everyone in the world needs me. They generously give me but never take me. What am I?
My teeth are sharp my back is straight to cut things up it is my fate.
A prisoner is told 'If you tell a lie we will hang you if you tell the truth we will shoot you.' What can the prisoner say to save himself?
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.