Which of the following is a characteristic test for the phenolic group?

Suppose the following reaction:
Benzene $(C_6H_6) + CH_3-CH=CH_2$ $\xrightarrow{H^{\oplus}} A$ $\xrightarrow{O_2} B$ $\xrightarrow{H^{\oplus} / \Delta} C + CH_3-CO-CH_3$
The structure of intermediate compound $B$ will be

Which of the following compounds has the most acidic nature?

The correct order of acid strength of the following compounds is:
$A$. Phenol
$B$. $p$-Cresol
$C$. $m$-Nitrophenol
$D$. $p$-Nitrophenol

Identify the correct set from the following:

Compound

$p K_a$

Product $(A)$ in this reaction is