Which of the following reagents can be used to oxidize $Butan-2-one$?

Reagent $X$ in the given reaction is:
(Image shows cyclohexanone being converted to cyclohexanol with a deuterium atom attached to the same carbon as the hydroxyl group.)

In the presence of dil. $HCl$,compound $A$ is converted to a constitutional isomer $(B)$. Compound $B$ is:

Benzaldehyde on heating with concentrated $NaOH$ gives:

Give the best conditions for this transformation:

When liquid $A$ is treated with a freshly prepared ammoniacal silver nitrate solution,it gives a bright silver mirror. The liquid forms a white crystalline solid on treatment with sodium hydrogensulphite. Liquid $B$ also forms a white crystalline solid with sodium hydrogensulphite but it does not give a test with ammoniacal silver nitrate. Which of the two liquids is an aldehyde? Write the chemical equations of these reactions also.