Which of the following methods can be used to oxidize $Butan-2-one$ to $Propionic \ acid$?

When ethanal $(CH_3CHO)$ and propanal $(CH_3CH_2CHO)$ undergo cross-aldol condensation with dilute $NaOH$, the pair of products obtained by cross-condensation reaction is:

The products $(A)$ and $(B)$ respectively in the above reaction are:

The reaction of $A$ to give $B$ and $C$ as shown in the reaction scheme is an example of:
$CH_2=CH_2$ $\xrightarrow[2. Zn/H_2O]{1. O_3} A$ $\xrightarrow{Conc. NaOH} B + C$
(Where $B$ is an alcohol and $C$ is a sodium salt of a carboxylic acid)

What are $X$ and $Y$ respectively in the following reactions?
$C_6H_5COOH \xrightarrow{X} C_6H_5CHO$
$C_6H_5CHO \xrightarrow[OH^-, 293 \ K]{C_6H_5COOH} Y \text{ (Major product)}$

Product $(D)$ will be