Product $(A)$ of the reaction is

Identify the reagent $R$ used in the following reaction:
$\text{Ketone} \xrightarrow{R} \text{Semicarbazone}$

What will be the order of reactivity of the following carbonyl compounds with a nucleophile?
$(I)$ $HCHO$
$(II)$ $CH_3CHO$
$(III)$ $(CH_3)_2CO$
$(IV)$ $(Me_3C)_2CO$

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

Arrange the following in the correct order of the rate of Nucleophilic Addition Reaction $(NAR)$:
$(I) \ HCHO$
$(II) \ CH_3CHO$
$(III) \ p-NO_2-C_6H_4CHO$
$(IV) \ p-CH_3-C_6H_4CHO$

Among the following compounds,which will react with acetone to give a product containing $> C = N -$?