Formaldehyde can be distinguished from acetaldehyde by the use of

$A$ carbonyl compound reacts with hydrogen cyanide $(HCN)$ to form cyanohydrin,which on hydrolysis forms a racemic mixture of $\alpha$-hydroxy acid. The carbonyl compound is:

Formaldehyde when treated with $KOH$ gives methanol and potassium formate. The reaction is known as

Organic products $A$ and $B$ are respectively -

Identify $(A)$ in the following reaction sequence:
$\mathop {(A)}\limits_{\text{gives positive iodoform Test}}$ $\xrightarrow[(ii) H^{+}, H_2O, (iii) \text{conc. } H_2SO_4/\Delta ]{(i) CH_3MgBr} (B)$ $\xrightarrow{O_3/Zn, H_2O}$

Which statement is incorrect for the given reaction sequence: $CH_3-CN$ $\xrightarrow[(2) H_2O]{(1) CH_3MgBr} X$ $\xrightarrow{2,4-DNP} Y$?