What is obtained when nitrobenzene is treated sequentially with $(i)$ $NH_4Cl / Zn$ dust and $(ii)$ $H_2SO_4 / Na_2Cr_2O_7$?

The products $X$ and $Y$ in the following reaction sequence are:

The compound $A$ with the following sequence of reactions gives benzoic acid.
$A$ $\xrightarrow{NaNO_2/HCl} B$ $\xrightarrow{KCN} C$ $\xrightarrow{H_3O^{+}} \text{benzoic acid}$
The compound $A$ is:

Phenyl isocyanides are prepared from which of the following reactions?

The major product formed in the following reaction is:

The correct order of basicities of the following compounds is:
$1. CH_3-C(=NH)NH_2$ (Acetamidine)
$2. (CH_3)_2NH$ (Dimethylamine)
$3. CH_3-CH_2-NH_2$ (Ethylamine)
$4. CH_3-CONH_2$ (Acetamide)