Which among the following represents reagent $A$ in the given reaction?
$C_6H_5N_2^+Cl^- + A \xrightarrow{NaOH} \text{Product (Orange-red dye)}$

An organic compound $A$ contains nitrogen and chlorine. It dissolves readily in water to give a solution that turns litmus red. Titration of compound $A$ with standard base indicates that the molecular weight of $A$ is $131 \pm 2$. When a sample of $A$ is treated with aqueous $NaOH$,a liquid separates which contains $N$ but not $Cl$. Treatment of the obtained liquid with nitrous acid followed by phenol gives an orange precipitate. The compound $A$ is:

Product $(E)$ is

Identify $A$ and $B$ in the following reaction sequence:
Aniline $\xrightarrow[KCN]{NaNO_2/HCl} (A)$ $\xrightarrow{SnCl_2/HCl/H_3O^+} (B)$

The product $(Y)$ of the following reaction is:

Primary and secondary amines can be distinguished by $:-$