Which of the following carbonyl compounds forms the most stable hydrate when $H_2O$ is added across the $C=O$ group?

Aldehydes that do not undergo aldol condensation are:
$1$. $CH_3CH_2CHO$ (propanal)
$2$. $Cl_3CCHO$ (trichloroethanal)
$3$. $HCHO$ (methanal)
$4$. $CH_3CHO$ (ethanal)
$5$. $C_6H_5CHO$ (benzaldehyde)

$A$ carbonyl compound $X$ $(C_8H_8O)$ undergoes disproportionation with conc. $KOH$ on heating. The product of $X$ with $Zn-Hg/HCl$ is $Y$ and the product of $X$ with $NaBH_4$ is $Z$. What are $Y$ and $Z$ respectively?

In the reaction,the acid obtained will be
$CH_3CHO + HCN \to CH_3CH(OH)CN \xrightarrow{H_2O} CH_3CH(OH)COOH$

Identify the name of the reaction when an aldehyde or ketone reacts with $Zn-Hg / \text{conc. } HCl$ to give an alkane.

In the given reaction,what is $y$?
$CH_3CH_2COCH_2COOH$ $\xrightarrow{\Delta} x$ $\xrightarrow[(ii) H_2O]{(i) LiAlH_4} y$