Which of the following substances cannot be used as a starting material for the preparation of iodoform?

What is an acetal? Give examples. $OR$ Give the reaction of ethanal with $(a)$ ethanol and $(b)$ ethylene glycol in the presence of dry $HCl$ gas.

Give the conversion of the following:
$(i)$ $but-2-enal$ from $ethanal$
$(ii)$ $Methyl$ $benzoate$ from $benzaldehyde$

Product $(A)$ is

An ester $(A)$ with molecular formula $C_9H_{10}O_2$ was treated with excess of $CH_3MgBr$ and the complex so formed was treated with $H_2SO_4$ to give an olefin $(B)$. Ozonolysis of $(B)$ gave a ketone with molecular formula $C_8H_8O$ which shows positive iodoform test. The structure of $(A)$ is

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