The conversion shown below can be brought about by?

What is the main product of the reaction between $2-methylpropene$ and $HBr$?

$cis-3-hexene \xrightarrow{(a)} \text{meso } 3,4-hexanediol$
$trans-3-hexene \xrightarrow{(b)} \text{meso } 3,4-hexanediol$
Choose the pair of reagents $(a, b)$ for the above conversions.

$A$ 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 :

Consider the following reaction:
$Alkene (A) \xrightarrow{KMnO_4, \Delta} CH_3CH_2COCH_3 + CH_3CH_2CH_2CH_2COOH$
$A$ is:

Predict the product$(s)$ obtained for the following reaction:
$3$-methylcyclopentene + $Br_2 / CCl_4 \rightarrow ?$