Which of the following undergoes nucleophilic substitution reaction according to the $S_{N}1$ mechanism?

An alkyl halide $X$ $(C_4H_9Br)$ undergoes nucleophilic substitution by $S_N2$ reaction. The product of $X$ on reaction with $Mg/\text{dry ether}$ followed by $D_2O$ is:

Which among the following is $NOT$ a correct statement about $S_{N}1$ reaction?

Chlorination of toluene in the presence of light and heat followed by treatment with aqueous $NaOH$ gives:

Number of moles of $AgCl$ formed in the following reaction is $X$. Identify $X$ from the given reaction.

Which one of the following has the highest boiling point?