Identify A and B in the chemical reaction.

$\Rightarrow$ 1st reaction Markovnikov's addition of $\mathrm{HCl}$ on double bond while ${\mathrm{2}}^{\mathrm{nd} }$ reaction is halide substitution by Finkelstein reaction.

Finkelstein reaction: An S_N2 reaction in which one halogen atom (the leaving group) is replaced by iodide (the nucleophile).