The correct structures of $A$ and $B$ formed in the following reactions are:

Arrange the given amines in decreasing order of their basicity.

Identify the reagents $A, B, C$ respectively in the following reaction sequence:

The correct statements about the products $B$ and $C$ in the given reactions are
$CH_3CH_2OH$ $\xrightarrow[\text{Anhy } ZnCl_2]{HCl} A$ $\xrightarrow[\text{AgCN}]{\text{ethanolic}} \underset{\text{Minor}}{B} + \underset{\text{Major}}{C}$
$I$. $B$ and $C$ are functional isomers
$II$. With $H_2 / \text{Catalyst}$,$B$ gives $1^{\circ}$ amine and $C$ gives $2^{\circ}$ amine
$III$. $B$ on acid hydrolysis gives formic acid and $C$ gives $C_3H_6O_2$
$IV$. $C$ forms isocyanate with $HgO$

Which of the following compounds has the lowest $pK_{b}$ value?

$A$. Phenyl methanamine
$B$. $N,N$-Dimethylaniline
$C$. $N$-Methylaniline
$D$. Benzenamine
Choose the correct order of basic nature of the above amines.