Mandelonitrile is obtained by the reaction between hydrogen cyanide and

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 $(B)$?

Find out the reactivity order of the labeled functional groups towards $LiAlH_4$ reduction.

When a nucleophile encounters a ketone,the site of attack is

An organic compound $A$ is oxidized using acidified $K_2Cr_2O_7$ solution to form compound $B$. Compound $B$ gives the $DNP$ test but not the silver mirror test. Then,compound $A$ is:

$m$-chlorobenzaldehyde on reaction with conc. $KOH$ at room temperature gives