Which of the following compounds undergoes nucleophilic substitution reaction most easily?

The correct increasing order of reactivity for the following molecules towards electrophilic aromatic substitution is:

In the following reaction:

The major product is:

Arrange the following compound in decreasing order of reactivity towards nucleophilic addition reaction:

$\left(\mathrm{I}\right)$ ${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{COCH}}_3$

$\left(\mathrm{II}\right)$ ${\mathrm{CH}}_3{\mathrm{COC}}_2{\mathrm{H}}_5$

$\left(\mathrm{III}\right)$ ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{CHO}$

$\left(\mathrm{IV}\right)$ ${\mathrm{ClCH}}_2\mathrm{CHO}$

What is the major product formed, when the following compound is treated with ${\mathrm{Br}}_2$ in the presence of ${\mathrm{FeBr}}_{\text{3}}$?