Which of the following has the highest value of $pK_b$?

In the reaction $RNH_2 + CHCl_3 + 3KOH(alc.) \rightarrow A + 3KCl + 3H_2O$,the product $A$ can be converted back to $RNH_2$ by which process?

In the reaction $CH_3NH_2 + X + KOH \rightarrow CH_3NC + 3KCl + 3H_2O$,what is $X$?

$C_6H_5CONHCH_3$ can be converted into $C_6H_5CH_2NHCH_3$ by

Nitration of aniline also gives $m$-nitroaniline in a strong acidic medium because:

The product formed when aniline is treated with chloroform in the presence of $KOH$ (alcoholic) is