Aniline when treated with $HNO_2$ and $HCl$ at $0\,^oC$ gives

The product $(A)$ is:

Find $A$ in the reaction $R-NH_2 + A \longrightarrow$ Schiff base.

Consider the reaction sequence from $P$ to $Q$ shown below. The overall yield of the major product $Q$ from $P$ is $75 \%$. What is the amount in grams of $Q$ obtained from $9.3 \ mL$ of $P$? (Use density of $P = 1.00 \ g \ mL^{-1}$,Molar mass of $C = 12.0, H = 1.0, O = 16.0$ and $N = 14.0 \ g \ mol^{-1}$)

The increasing basicity order of the following compounds is:
$(1)$ $CH_3CH_2NH_2$
$(2)$ $(CH_3CH_2)_2NH$
$(3)$ $(CH_3)_3N$
$(4)$ $PhNHCH_3$

Highest value of $pK_b$ will be of :