Arrange the following in decreasing order of electrophilicity of carbonyl carbon.

In the given transformation,which of the following is the most appropriate reagent?

$3$-hydroxybutanal is formed when $(X)$ reacts with $(Y)$ in a dilute $(Z)$ solution. What are $X, Y$ and $Z$?

The reagent used in the Wolff-Kishner reduction is

How can $A$ and $B$ be differentiated?

$A$ 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 $3.$