In the given reaction sequence,identify the processes $X$ and $Y$ respectively to obtain salicylaldehyde from chlorobenzene:
$Chlorobenzene$ $\xrightarrow{X} Phenol$ $\xrightarrow{Y} Salicylaldehyde$

Which of the following is the most acidic?

The common name of $Benzene-1,4-diol$ is

Product $(A)$ and $(B)$ respectively are :-

One mole of phenol is treated with dilute $HNO_3$ at $298 \ K$ to give a mixture of products. The mixture is separated by steam distillation. The steam volatile compound $(X)$ is separated. The increase in percentage of oxygen in $(X)$ with respect to phenol is . . . . . . $\times 10^{-1}$ %. (Given molar mass in $g \ mol^{-1}$: $H:1, C:12, N:14, O:16$)

An organic compound $(C_8H_{10}O_2)$ rotates plane-polarized light. It produces a pink color with a neutral $FeCl_3$ solution. What is the total number of all the possible isomers for this compound?