The following reaction gives:

Compound $x$ having molecular formula $C_3H_6O$ is reduced by Red $P/HI$ to give compound $y$ $(C_3H_8)$. Since $x$ reduces Tollen's reagent,what is the possible structure of $x$?

Least reactive towards nucleophilic addition is

The structure of $(R)$ is:

Two aliphatic aldehydes $P$ and $Q$ react in the presence of aqueous $K_2CO_3$ to give compound $R$,which upon treatment with $HCN$ provides compound $S$. On acidification and heating,$S$ gives the product shown below:
$1.$ The compounds $P$ and $Q$ respectively are:
$2.$ The compound $R$ is:
$3.$ The compound $S$ is:
Give the answer for questions $1$,$2$ and $3$.

$C_2H_5CHO$ and $(CH_3)_2CO$ can be distinguished by testing with