Aniline on treatment with $\text{NaNO}_2$ / HCl at about $0^\circ\text{C}$ gives a compound A, which on further treatment with CuCN / KCN gives a compound B, which when reacts with $\text{H}_2$ / Ni gives a compound C. The compound C on reaction with $\text{HNO}_2$ gives a compound D. The structure of D is:

Identify the reagent used to distinguish primary and secondary amines by Hinsberg test.

Identify the substrate 'A' in the following reaction.
$\text{A} \xrightarrow[\large{\text{ii)}\ \Delta}]{\large{\text{i) Moist Ag}_2\text{O}}} \text{CH}_3\text{CH}_2\text{N(CH}_3)_2 + \text{CH}_2 = \text{CH}_2$

Identify the product B in following reaction.
$\text{CH}_3\text{Br} \xrightarrow{\large{\text{KCN}}} \text{A} \xrightarrow[\large{\text{C}_2\text{H}_5\text{OH}}]{\large{\text{Na}}} \text{B}$