The hydrogen atom bonded to the carbon designated by which number in $\stackrel{4}{C}H_3-\stackrel{3}{C}H_2-\stackrel{2}{C}H_2-\stackrel{1}{C}HO$ is most acidic?

Match the example given in Column-$I$ with the name of the reaction in Column-$II$.

Column-$I$ (Example)	Column-$II$ (Reaction)
$(A)$ $CH_3COCl + H_2 \xrightarrow{Pd-C/BaSO_4} CH_3CHO$	$(1)$ Friedel-Crafts acylation
$(B)$ $C_6H_5CHO \xrightarrow{NaOH} C_6H_5CH_2OH + C_6H_5COONa$	$(2)$ $HVZ$ reaction
$(C)$ $C_6H_6 + CH_3COCl \xrightarrow{AlCl_3} C_6H_5COCH_3$	$(3)$ Aldol condensation
$(D)$ $R-CH_2COOH \xrightarrow{Br_2/Red P} R-CH(Br)COOH$	$(4)$ Cannizzaro's reaction
$(E)$ $CH_3-CN \xrightarrow{SnCl_2/HCl, H_2O/H^+} CH_3-CHO$	$(5)$ Rosenmund's reduction
$(F)$ $2CH_3CHO \xrightarrow{NaOH} CH_3-CH=CH-CHO$	$(6)$ Stephen's reaction

Given below are two statements:
Statement $I$: $2, 6$-diethylcyclohexanone and $6$-methyl-$2$-$n$-propylcyclohexanone are metamers.
Statement $II$: $2, 2, 6, 6$-tetramethylcyclohexanone exhibits keto-enol tautomerism.

In the reaction,$[X]$ will be:

$A \xrightarrow{} (CH_3)_2C=CH-CO-CH_3$. $A$ is:

When $(X)$ reacts with $(Y)$ in the presence of dilute $(Z)$ solution,$3-$hydroxybutanal is formed. What are $(X), (Y),$ and $(Z)$?