The action of diazomethane on phenol liberates which of the following gases?

In the reaction sequence,phenol reacts with $HNO_2$ to form $X$,which then reacts with phenol in the presence of $H_2SO_4$ to form $Y$. Identify the major products $X$ and $Y$.

When phenol is treated with $D_{2}SO_{4} / D_{2}O$, some of the hydrogens get exchanged. The final product in this exchange reaction is

Benzene $+ CH_3CH_2CH_2Cl$ $\xrightarrow{AlCl_3} M$ $\xrightarrow{(i) O_2/\Delta , (ii) H_3O^+} N + \text{phenol}$. Here $M$ and $N$ are

Which of the following is the most acidic compound?

What will be the product $X$ in the following reaction?