Silver mirror is a test for

In the given set of reactions,identify $D$:
$CH_3COOH$ $\xrightarrow{SOCl_2} A$ $\xrightarrow[Anhy. AlCl_3]{Benzene} B$ $\xrightarrow{HCN} C$ $\xrightarrow{H_2O} D$

An organic compound $(A)$ with molecular formula $C_8H_8O$ forms an orange-red precipitate with $2,4-DNP$ reagent and gives a yellow precipitate on heating with iodine in the presence of sodium hydroxide. It neither reduces Tollens' or Fehlings' reagent,nor does it decolourise bromine water or Baeyer's reagent. On drastic oxidation with chromic acid,it gives a carboxylic acid $(B)$ having molecular formula $C_7H_6O_2$. Identify the compounds $(A)$ and $(B)$ and explain the reactions involved.

What are $X$,$Y$,and $Z$ in the following reaction sequence respectively?
Benzene $\xrightarrow{X}$ Benzaldehyde $\xrightarrow{\text{Conc. NaOH}, \Delta} Y + Z$

Correct order for nucleophilic addition reaction :
$(1)$ $C_{6}H_{5}COC_{6}H_{5}$
$(2)$ $C_{6}H_{5}CHO$
$(3)$ $p-CH_{3}C_{6}H_{4}CHO$
$(4)$ $p-CH_{3}OC_{6}H_{4}CHO$

Which statement is incorrect for the given reaction sequence: $CH_3-CN$ $\xrightarrow[(2) H_2O]{(1) CH_3MgBr} X$ $\xrightarrow{2,4-DNP} Y$?