In the reaction sequence $CH_3CH = CHCH_3$ $\xrightarrow{O_3} A$ $\xrightarrow{H_2O/Zn} B$,the alkene forms product $B$. What is product $B$?

$(R)-3-$bromocyclopentene (shown below) reacts with $Br_2/CCl_4$ to form two products,$Y$ and $Z$. $Y$ is not optically active (does not rotate plane-polarized light). What is the structure of $Y$?

$CH_3-CH(CO_2K)-CH(CO_2K)-CH_3 \xrightarrow{\text{electrolysis}} (A) \text{ (Major)}$
The major product $(A)$ of the above reaction is:

$A$ 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 :

Assertion $(A)$: Reaction of $but-1-ene$ with $HBr$ gives $1-bromobutane$ as the major product.
Reason $(R)$: Addition of $HBr$ to unsymmetrical alkenes proceeds according to Markovnikov's rule.
The correct answer is

What is the product obtained when phenylethene is treated with $KMnO_4$ in dilute $H_2SO_4$?