What is the product formed when an aliphatic primary amine reacts with $HNO_2$?

Among the following compounds,the increasing order of their basic strength is

Which of the following reaction names is not associated with a scientist?

Which of the following substances is more basic than aniline?

Give the structure of $A$ in the following reaction.
$2\text{-Nitro-4-methylaniline} \xrightarrow[(ii) \ H_3PO_2, H_2O]{(i) NaNO_2 + HCl, 273 - 278 \ K} A$.

The final major product of the following reaction is: