Which one of the following compounds when heated with $KOH$ and a primary amine gives the carbylamine test?

Which is the correct decreasing order of basic strength for the following compounds?
$(I)$ Aniline
$(II)$ $p$-Nitroaniline
$(III)$ $p$-Cyanoaniline
$(IV)$ $p$-Toluidine

When aniline reacts with $NaNO_2$ and dil. $HCl$ at $0^{\circ} - 5^{\circ}C,$ the product formed is

Among the isomeric amines,select the one with the lowest boiling point.

Which from the following amines has the highest $pK_{b}$ value?

Identify the compound that will react with Hinsberg's reagent to give a solid which dissolves in alkali.