Question

why benzene ring cannot give addition reaction as an alkene?

Answer 1

Benzene ring forms the most stable compound with the resonating structure with double bonds
Being an cyclo alkene, its double bond makes a resonating structure which makes it each bond stronger than before. Thus, as it is stronger it dont react with any reagent and breaks the double bond.
So benzene ring cannot give addition reaction as an alkene.

Hope I helped u.

Answer 2

then benzene ring cannot give addition reaction as an alkene