Answer:
I am so delicate that even mentioning me breaks me. What am I?
Goes over all the hills and hollows, Bites hard, but never swallows.
I am between earth and heaven. What am I?
With a halo of water and a tongue of wood, stone as skin long I stood. What am I?
Of the king I am blue and of the peasant I am red. Of the frog I am cold and of the dog I am hot instead.
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.