Which of the following will be most readily dehydrated in acidic conditions?

What are $X$ and $Y$ respectively in the following reactions?
$C_6H_5COOH \xrightarrow{X} C_6H_5CHO$
$C_6H_5CHO \xrightarrow[OH^-, 293 \ K]{C_6H_5COOH} Y \text{ (Major product)}$

The reaction is given as follows: $(CH_3)_2CHCHO + CH_3MgBr$ $\xrightarrow{Ether} A$ $\xrightarrow{H_3O^+} B$. The $IUPAC$ name of $B$ is:

$(CH_3)_3CCHO$ does not undergo aldol condensation due to

How will you convert butan-$2$-one to propanoic acid?
$CH_3-CH_2-CO-CH_3 + I_2 + NaOH$ $\rightarrow C_2H_5CO_2^-Na^+ + CHI_3$ $\xrightarrow{H^+} C_2H_5COOH$

The reaction sequence is as follows:
Benzene + $CH_3COCl$ $\xrightarrow{\text{Anhydrous } AlCl_3} (A)$ $\xrightarrow{(x)} \text{Ethylbenzene}$.
Reagent $(x)$ can be: