Is a benign tumor considered to be cancer?

no. (more info below)

Explanation:

a benign tumor does not interfere or invade nearby tissue or spread to other parts of the body the way cancer can. a tumor is simply an abnormal growth of cells that serves no purpose

hope this helped!

sheep is a herbivore animal whereas grasshopper belongs to the class chordates but both of them feed on greens.  

if grasshopper and sheep feeding on a pasture land, i do not think both of them will have any impact on each other. however, the number of the species can make difference. since sheep feed on greens, there is a possibility there left no pasture land for the grasshoppers or they may get extinct.