Which of the following amines is the weakest base?

The correct statements of the following are:
$A$. Aniline forms a stable benzene diazonium chloride at $285 \ K$.
$B$. $N$-Phenylethanamide is less reactive towards nitration than aniline.
$C$. $p-CH_3C_6H_4COCl$ is Hinsberg reagent.

Identify substrate $A$ in the following reaction.
$A + AgOH \xrightarrow[ii) \Delta]{i) \text{moist } Ag_2O} CH_3CH_2N(CH_3)_2 + CH_2=CH_2$

Suppose the following reaction:
$CH_3-CH(CH_3)-COOH + CH_3-NH_2$ $\rightarrow 'A'$ $\xrightarrow{\Delta} 'B'$ $\xrightarrow{LiAlH_4 (excess)} 'C'$
The final product '$C$' will be:

Why is $m$-nitroaniline obtained from the nitration of aniline in a strongly acidic medium?

Nitrosobenzene can be prepared by oxidizing aniline with which of the following reagents?