$CH_3-CHO + HCN \to A$; Compound $A$ on hydrolysis gives

What are $X$ and $Y$ in the following reaction sequence?
$Propene$ $\xrightarrow{HBr} A$ $\xrightarrow[Dry \ ether]{Mg} B$ $\xrightarrow[2. H_3O^{+}]{1. X} Y$

Benzyl alcohol and sodium benzoate are obtained by the action of sodium hydroxide on benzaldehyde. This reaction is known as

$A$ compound gives a positive test with $I_2/NaOH$ and is extracted from benzene by saturated $NaHSO_3$. It may be

Paraldehyde is

An alkene $(A)$ $C_{16}H_{16}$ on ozonolysis gives only one product $(B)$ $C_8H_8O$. $(B)$ can also be obtained by the hydrolysis of the product obtained from the reaction between cyanobenzene and $CH_3MgBr$. $(A)$ shows geometrical isomerism and decolourises $Br_2$ water. $(B)$ on treatment with $SeO_2$ produces $(C)$. Which statement is not correct about $(B)$?