Arrange the following compounds in their decreasing order of reactivity towards nucleophilic addition reaction: $CH_3COCH_3$,$CH_3COC_2H_5$,$CH_3CHO$.

Which of the following substances will not give a brick-red precipitate with Fehling's solution?

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 . . . .

$A$ carbonyl compound reacts with hydrogen cyanide $(HCN)$ to form cyanohydrin,which on hydrolysis forms a racemic mixture of $\alpha$-hydroxy acid. The carbonyl compound is:

The product $A$ in the above reaction is

The major product formed in the following reaction is: