Which of the following is the most stable?

$A$ compound $A$ on reaction with $X$ and $Y$ produces the same major product but different by-products $a$ and $b$. Oxidation of $a$ gives a substance produced by ants.
$X$ and $Y$ respectively are :

Butane can be prepared from butene by reaction with........

Give the chemical reactions for the following conversions:
$(1)$ Glyoxal from acetylene
$(2)$ Glycol from bromoethane

What is the product formed when ethylene reacts with $1\%$ cold alkaline $KMnO_4$?

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R.$
Assertion $A :$ Treatment of bromine water with propene yields $1-$bromopropan$-2-$ol.
Reason $R:$ Attack of water on bromonium ion follows Markovnikov rule and results in $1-$bromopropan$-2-$ol.
In the light of the above statements,choose the most appropriate answer from the options given below: