Identify the final product in the following reaction sequence: $R-CHO$ $\xrightarrow{HS-(CH_2)_3-SH}$ $\xrightarrow{n-BuLi}$ $\xrightarrow{D_2O}$ $\xrightarrow{HgCl_2/CdCO_3, H_2O} \text{Product}$

The compound formed when propanone is made to react with ethyl magnesium bromide followed by hydrolysis is

Geminal diols (compounds with two $-OH$ groups on the same carbon atom) are generally unstable. However,which of the following is stable?

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 $3$.

$A$ carbonyl compound $P$,which gives a positive iodoform test,undergoes reaction with $MeMgBr$ followed by dehydration to give an olefin $Q$. Ozonolysis of $Q$ leads to a dicarbonyl compound $R$,which undergoes intramolecular aldol reaction to give predominantly $S$.
$P$ $\xrightarrow[\substack{2. H^{+}, H_2 O \\ 3. H_2 SO_4, \Delta}]{1. MeMgBr} Q$ $\xrightarrow[2. Zn, H_2 O]{1. O_3} R$ $\xrightarrow[2. \Delta]{1. OH^{-}} S$
$1.$ The structure of the carbonyl compound $P$ is
$2.$ The structures of the products $Q$ and $R$,respectively,are
$3.$ The structure of the product $S$ is
Give the answer for questions $1, 2$ and $3.$

Predict the products of the following reactions with $CH_3CHO$:
$(i) CH_3CHO + C_6H_5MgBr$
$(ii) CH_3CHO + C_6H_{11}MgBr$
$(iii) CH_3CHO + (CH_3)_2CHMgBr$
Followed by acidic hydrolysis in each case.