The compound which undergoes $S_{N^1}$ reaction most rapidly is

Arrange the following in the correct order of reactivity towards $S_{N}2$ reaction:
$I$: $1$-Chloropropane
$II$: $2$-Chloropropane
$III$: $1$-Iodopropane
$IV$: $2$-Iodopropane

The correct description of the product in the following reaction is:
$CH_3-CH(Br)-CH_2OCH_3 \text{ } ((R)) \xrightarrow{NaCN, \text{acetone}} CH_3-CH(CN)-CH_2OCH_3$

The major product obtained in the reaction of $1$-phenyl-$2$-bromobutane with $NaOMe$ is:

$C_6H_6 + CH_3CH_2CH_2Cl + AlCl_3 \to X$ (Major product)
$X$ (Major product) $\xrightarrow{HNO_3 + H_2SO_4} Y$ (Major product) $\xrightarrow{Sn + HCl} Z$ $\xrightarrow{H_2SO_4 + SO_3} W$
$W$ is

The best method for the preparation of $Me_{3}CCN$ is