Which of the following will not give the iodoform test?

Which of the following compounds is used to convert acetaldehyde into acetaldehyde cyanohydrin?

The compound $(X)$ in the given reaction is:

Which of the following will fail to react with potassium dichromate and dilute sulphuric acid?

Which of the following reactions converts the carbonyl group of aldehydes and ketones to a methylene group on treatment with zinc amalgam and concentrated $HCl$?

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 . . . .