The following reaction belongs to $(CH_3)_3CBr \xrightarrow{H_2O} (CH_3)_3COH$.

$C_4H_9Cl$ (Optically Active Compound $A$) $\xrightarrow[DMSO]{NaCN}$ $(R)-2-$methylbutanenitrile; Identify compound $A$?

Which is the correct decreasing order of boiling points for the following compounds?

Two bottles containing $C_6H_5I$ and $C_6H_5CH_2I$ have lost their original labels. They are labeled as $A$ and $B$ for testing. $A$ and $B$ are taken separately in test tubes and boiled with $NaOH$ solution. The final solution of each test tube is acidified with dilute $HNO_3$ and a little $AgNO_3$ is added. Solution $B$ gives a yellow precipitate. Which of the following statements is correct?

Select the reagent that will yield the greater amount of substitution on reaction with $CH_3CH_2Br$.

Differentiate between the $S_N2$ and $S_N1$ mechanisms of alkyl halides.