(A) Saturated compound is converted into unsaturated compound by removal of group of atoms hence, it is an elimination reaction.

(B) —Br group is replaced by —OH group hence, it is a substitution reaction.

(C) Addition of Br₂ converts an unsaturated compound into a saturated compound hence, it is an addition reaction.

$$\alpha $$-hydrogen at bridge carbon never participates in tautomerism. Thus, only (III) exhibits tautomerism.

The given structure has 18$$\sigma $$ bonds and 2$$\pi $$ bonds.