What is the major product of the following reaction? $C_2H_5-CONH_2$ $\xrightarrow{Br_2 / KOH} A$ $\xrightarrow{CHCl_3 / KOH} \text{Major Product}$

The product $(B)$ is:

The compounds $X$ and $Y$ are respectively:

$A$ is a neutral organic compound $(M.F.: C_8H_9ON)$. On treatment with aqueous $Br_2 / HO^{(-)}$, $A$ forms a compound $B$ which is soluble in dilute acid. $B$ on treatment with aqueous $NaNO_2 / HCl$ $(0-5^{\circ}C)$ produces a compound $C$ which on treatment with $CuCN / NaCN$ produces $D$. Hydrolysis of $D$ produces $E$ which is also obtainable from the hydrolysis of $A$. $E$ on treatment with acidified $KMnO_4$ produces $F$. $F$ contains two different types of hydrogen atoms. The structure of $A$ is

$A$ trinitro compound,$1,3,5$-tris-($4$-nitrophenyl)benzene,on complete reaction with an excess of $Sn/HCl$ gives a major product,which on treatment with an excess of $NaNO_2/HCl$ at $0^{\circ} C$ provides $P$ as the product. $P$,upon treatment with excess of $H_2O$ at room temperature,gives the product $Q$. Bromination of $Q$ in aqueous medium furnishes the product $R$. The compound $P$ upon treatment with an excess of phenol under basic conditions gives the product $S$.
The molar mass difference between compounds $Q$ and $R$ is $474 \ g \ mol^{-1}$ and between compounds $P$ and $S$ is $172.5 \ g \ mol^{-1}$.
$(1)$ The number of heteroatoms present in one molecule of $R$ is . . . . .
[Use: Molar mass (in $g \ mol^{-1}$): $H=1, C=12, N=14, O=16, Br=80, Cl=35.5$
Atoms other than $C$ and $H$ are considered as heteroatoms]
$(2)$ The total number of carbon atoms and heteroatoms present in one molecule of $S$ . . . . . .
[Use: Molar mass in $g \ mol^{-1}$]: $H=1, C=12, N=14, O=16, Br=80, Cl=35.5$
Atoms other than $C$ and $H$ are considered as heteroatoms
Give the answer for question $(1)$ and $(2)$.

Complete the following reactions:
$(i)$ $C_{6}H_{5}NH_{2} + CHCl_{3} +$ alc. $KOH \rightarrow$
$(ii)$ $C_{6}H_{5}N_{2}Cl + H_{3}PO_{2} + H_{2}O \rightarrow$
$(iii)$ $C_{6}H_{5}NH_{2} + H_{2}SO_{4}$ (conc.) $\rightarrow$
$(iv)$ $C_{6}H_{5}N_{2}Cl + C_{2}H_{5}OH \rightarrow$
$(v)$ $C_{6}H_{5}NH_{2} + Br_{2(aq)} \rightarrow$
$(vi)$ $C_{6}H_{5}NH_{2} + (CH_{3}CO)_{2}O \rightarrow$
$(vii)$ $C_{6}H_{5}N_{2}Cl \xrightarrow[(ii) NaNO_{2}/Cu, \Delta ]{(i) HBF_{4}}$