The formation of cyanohydrin from ketones is an example of which type of reaction?

The correct statement regarding a carbonyl compound with a hydrogen atom on its $\alpha$-carbon is

Acetaldehyde forms a white crystalline precipitate on mixing with a ...... solution of

Which of the following reagents can be used for the given chemical transformation?

Toluene $\xrightarrow[(2) \ H_3O^{+}]{(1) \ CrO_2Cl_2 / CS_2} X$ $\xrightarrow{\text{Conc. } NaOH} Y + Z$. The correct statements about $Y$ and $Z$ are:
$A. \quad Y$ is a secondary alcohol
$B. \quad Y$ is the reduction product of $X$
$C. \quad Z$ on heating with soda lime gives benzene
$D. \quad Y$ does not give $H_2$ gas with $Na$ metal

Arrange the following compounds in the increasing order of their reactivity towards the nucleophilic addition of $HCN$:
$1. HCHO$
$2. CH_3COCH_3$
$3. PhCOCH_3$
$4. PhCOPh$