Which among the following compounds is the weakest base?

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

The major product obtained in the reaction of aniline with acetic anhydride is

Identify the products $y$ and $x$ in the following reaction sequence:
$C_6H_5CONH_2 \xrightarrow{NaOBr} y$
$C_6H_5CONH_2 \xrightarrow[(ii) H_3O^+]{(i) C_6H_5SO_2Cl / py, \Delta} x$

What is the product $(X)$ in the reaction $C_6H_5NH_2 + HCl + NaNO_2 \rightarrow (X)$?

In the carbylamine reaction,the number of moles of $KOH$ and $CHCl_3$ used per mole of isocyanide produced are $X_1$ and $X_2$ respectively. Find out $X_1 - X_2$.