Which of the following reactions will yield benzaldehyde as a product?

Consider the following reactions:
$C_2H_2 + H_2O \xrightarrow[333 \ K]{Hg^{2+} / H^{+}} [X] \stackrel{\text{Isomerisation}}{\rightleftharpoons} Y$
$Y$ cannot be obtained from which of the following reactions?

Predict the product of the following reaction:
$m\text{-Tolunitrile} \xrightarrow[(ii) H_3O^+]{(i) CH_3MgBr} \text{Product}$

In the reaction $RMgBr + HC(OEt)_3 \xrightarrow{Ether, H_3O^{+}} P$, the product $P$ is

Reaction: $CH_3OH + O_2 \xrightarrow{600\,^oC, \text{Ag}} \text{Product}$. The product is:

In the following sequence of reactions:
$C_6H_5CH_3$ $\xrightarrow{KMnO_4} A$ $\xrightarrow{SOCl_2} B$ $\xrightarrow{H_2/Pd, BaSO_4} C$
the product $C$ is: