Which one of the following will give a primary amine on hydrolysis?

Which of the following is the strongest base?

How many metamers are possible for the molecular formula $C_4H_{11}N$?

The reaction of $N,N'$-diphenylthiourea with concentrated $HCl$ upon heating is given by:
$(C_6H_5NH)_2C=S \xrightarrow{conc. HCl, Heat} A + B$
The unknown compounds $A$ and $B$ in the above reaction are:

The product of the following reaction is:

Aniline when treated with $HNO_2$ and $HCl$ at $0\,^oC$ gives