An organic compound with the molecular formula $C_9H_{10}O$ forms a $2,4-DNP$ derivative,reduces Tollen's reagent and undergoes Cannizzaro reaction; on vigorous oxidation it gives $1,2-$benzenedicarboxylic acid. The structure of the organic compound is:

Which of the following react with $NaHSO_3$?

Reaction of iso-propylbenzene with $O_2$ followed by treatment with $H_3O^{+}$ forms phenol and a by-product $P$. Reaction of $P$ with $3$ equivalents of $Cl_2$ gives compound $Q$. Treatment of $Q$ with $Ca(OH)_2$ produces compound $R$ and calcium salt $S$. The correct statement(s) regarding $P, Q, R$ and $S$ is(are):
$(A)$ Reaction of $P$ with $R$ in the presence of $KOH$ gives chloritone.
$(B)$ Reaction of $R$ with $O_2$ in the presence of light gives phosgene gas.
$(C)$ $Q$ reacts with aqueous $NaOH$ to produce $Cl_3CCH_2OH$ and $Cl_3CCOONa$.
$(D)$ $S$ on heating gives $P$.

$CH_3CH=CHCHO$ is oxidized to $CH_3CH=CHCOOH$ using

$CH_3CHO \xrightarrow{LiAlH_4} CH_3CH_2OH$
Which nucleophile is added in this reaction?

The structure of $(R)$ is: