The major product of the following reaction is:

An organic compound $P$ having molecular formula $C_6H_6O_3$ gives a ferric chloride test and does not have an intramolecular hydrogen bond. The compound $P$ reacts with $3$ equivalents of $NH_2OH$ to produce oxime $Q$. Treatment of $P$ with excess methyl iodide in the presence of $KOH$ produces compound $R$ as the major product. Reaction of $R$ with excess iso-butylmagnesium bromide followed by treatment with $H_3O^{+}$ gives compound $S$ as the major product. The total number of methyl $(-CH_3)$ groups in compound $S$ is . . . .

The reaction $2CH_3COOC_2H_5 \xrightarrow{C_2H_5ONa} CH_3COCH_2COOC_2H_5 + C_2H_5OH$ is called:

The final product of the following reaction contains:
$CH_3 - C \equiv C - CH_2 - COCl \xrightarrow[BaSO_4]{H_2 - Pd}$

An organic compound $X$ is oxidised by using acidified $K_2Cr_2O_7$ solution. The product obtained reacts with phenyl hydrazine but does not give the silver mirror test. The compound $X$ is,

What are $A$,$B$,and $C$ in the following reactions?