Ethyl bromide reacts with lead-sodium alloy to form

Identify the correct order of reactivity for the reaction with alcoholic $KOH$ for the following compounds:
$(a)$ $2$-bromo-$2,3$-dimethylbutane
$(b)$ $2$-chlorobutane
$(c)$ $2$-bromobutane
$(d)$ $1$-bromopropane

The correct order for increasing reactivity towards $S_N1$ substitution for the following compounds is:
$1. CH_3CH_2Br$
$2. CH_2=CHCH(Br)CH_3$
$3. CH_2=CHBr$
$4. CH_3CH(Br)CH_3$

Which of the following isomers of $C_4H_9Br$ is a chiral molecule?

In the reaction $2CHCl_3 + O_2 \xrightarrow{X} 2COCl_2 + 2HCl$,$X$ represents:

In which case is the formation of $butanenitrile$ possible?