The major product $(A)$ of the following reaction is:

Which compound undergoes nucleophilic substitution with $NaCN$ at the fastest rate?

Examine the following statements pertaining to an $S_N2$ reaction:
$(1)$ The rate of reaction is independent of the concentration of the nucleophile.
$(2)$ The nucleophile attacks the $C$ atom on the side of the molecule opposite to the group being displaced.
$(3)$ The reaction proceeds with simultaneous bond formation and bond rupture/cleavage.
Amongst the following,which of the above are true?

Consider the reactions.
$(i) \ (CH_3)_2CH-CH_2Br \xrightarrow{C_2H_5OH} (CH_3)_2CH-CH_2OC_2H_5 + HBr$
$(ii) \ (CH_3)_2CH-CH_2Br \xrightarrow{C_2H_5O^-} (CH_3)_2CH-CH_2OC_2H_5 + Br^-$
The mechanisms of reactions $(i)$ and $(ii)$ are respectively:

$n$-propyl bromide on treatment with ethanolic potassium hydroxide produces

Which among the following halides will generate the most stable carbocation in a nucleophilic substitution reaction?