Which of the following compounds has the lower boiling point?

Consider the reaction sequence shown below:
$Br-CH_2-CHO$ $\xrightarrow[\text{dry } HCl \text{ gas}]{\text{EtOH (excess)}} A$ $\xrightarrow{^tBuO^-K^+} B$
[Where $Et \Rightarrow -C_2H_5$,$^tBu \Rightarrow (CH_3)_3C^-$]
Identify the major products $A$ and $B$ formed respectively.

The correct order of rates of $C-Br$ bond ionisation of the following bromides is

$CH_3-CH_2-CH_2-Cl$ $\xrightarrow{KOH_{(aq)}} X$ $\xrightarrow{H^{+}/\Delta} Y$ $\xrightarrow{Cl_2/H_2O} Z$ (Major); $Z$ is

Which of the following pairs of compounds on heating gives butanenitrile?

Which compound undergoes nucleophilic substitution with $NaCN$ at the fastest rate?