Explain the conversion of diazo group into carboxylic group.

The final product $\mathrm{R}$ is

Identify $\mathrm{A}$ and $\mathrm{B}$.

In the sequence of the following reactions:

The starting compound '$\mathrm{P}$' is ______.

Give a chemical test to distinguish between these pairs of compounds.

Aniline and benzylamine.

Benzene azo-$\mathrm{\beta }$naphthol is an orange red dye widely used in textile industry for dyeing purpose. What are the structures of the reactants needed to prepare this dye?

Phenol on reaction with benzenediazonium chloride forms orange dye.