What does phenol give with dilute $HNO_3$?

Which of the following phenols has the largest $pK_a$ value (i.e.,is least acidic)?

The increasing order of $pKa$ values of the following compounds is:

Which is the final product of the Reimer-Tiemann reaction?

Which one of the following statements is not correct?

Arrange the following phenols in decreasing order of their $pK_{a}$ values:
$(A)$ Phenol
$(B)$ ortho-Nitrophenol
$(C)$ meta-Nitrophenol
$(D)$ para-Nitrophenol