$CH_3-CHO \xrightarrow{NaOH + Cl_2} A + HCOONa$. Product $A$ can be used as:

Grignard reagent is added to .......

The mixed aldol products obtained from the aldol condensation of ethanal $(CH_3CHO)$ and propanone $(CH_3COCH_3)$ are:

The aldehydes which will not form a single Grignard product with one equivalent of Grignard reagent are:
$(a)$ Benzaldehyde
$(b)$ $4$-Formylbenzoic acid
$(c)$ $4$-Methoxybenzaldehyde
$(d)$ $4$-(Hydroxymethyl)benzaldehyde

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 $P$.

Which of the following is the Wolff-Kishner reduction?