The reaction of $50\%$ aq $KOH$ on an equimolar mixture of $4-$methylbenzaldehyde and formaldehyde followed by acidification gives

Which of the following does not effect the transformation shown below?
$R_2C=O \rightarrow R_2CH_2$

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$:
Assertion $A$: Acetal/Ketal is stable in basic medium.
Reason $R$: The high leaving tendency of alkoxide ion gives the stability to acetal/ketal in basic medium.
In the light of the above statements,choose the correct answer from the options given below:

In the given reaction,what will be $A$ and $B$ respectively?
$(CH_3)_2CO$ $\xrightarrow{NaCN/HCl} A$ $\xrightarrow{H_3O^+} B$

From the compounds given below,the number of compounds which give a positive Fehling's test is:
Benzaldehyde,Acetaldehyde,Acetone,Acetophenone,Methanal,$4$-nitrobenzaldehyde,cyclohexane carbaldehyde.

$P \xrightarrow{H_2 / Pd-BaSO_4} Q \xrightarrow{(i) \text{ conc. } NaOH} R + S$. $R$ and $S$ form benzyl benzoate when treated with each other. Hence,$P$ is