The compound that will undergo $S_N 1$ reaction with the fastest rate is

Given below are two statements:
Statement-$I$: High concentration of strong nucleophilic reagent with secondary alkyl halides which do not have bulky substituents will follow $S_{N}2$ mechanism.
Statement-$II$: $A$ secondary alkyl halide when treated with a large excess of ethanol follows $S_{N}1$ mechanism.
In the light of the above statements,choose the most appropriate from the options given below:

An organic compound $X$ $(C_7H_7Cl)$ when reacted with $KCN$ in $C_2H_5OH$ gives a major product $Y$. $Z$ is formed when $Y$ is reduced with $LiAlH_4$. What are $Y$ and $Z$?

The reaction of ethyl bromide with lead-sodium alloy gives ......... .

What is the relative rate of $S_{N}1$ reaction for $(CH_{3})_{2}CHBr$?

The reaction of an alkyl halide with $Mg$ in dry ether produces ..... as the product.