Which of the following is called as Mandelonitrile?

Which of the following compounds can show an aldol condensation reaction?

The molecular formula of compound $A$ is $C_2Cl_3OH$. It reduces Fehling's solution and on oxidation gives a monocarboxylic acid $B$. Compound $A$ is obtained by the reaction of chlorine with ethyl alcohol. What is $A$?

Base-catalyzed aldol condensation occurs with:

Identify the final product of the following reaction sequence:
$o$-Phthalaldehyde $\xrightarrow{\text{OH}^-} A$ $\xrightarrow{\text{H}^+, \Delta} ?$

$3$-hydroxybutanal is formed when $(X)$ reacts with $(Y)$ in dilute $(Z)$ solution. What are $X, Y$ and $Z$?