What is the number of $\sigma$ bonds in $1$-butene?

Identify products $A$ and $B$ in the following reaction sequence:
$1$-methylcyclopentene $\xrightarrow{\text{dil. } KMnO_4, 273 \ K} A$ $\xrightarrow{CrO_3} B$

Baeyer's reagent is used in the laboratory for

The stereochemistry of the product formed in the following reaction is:

Ethylene is a member of the $.....$ series.

Assertion : Addition of $HBr$ on $2-$butene gives two isomeric products.
Reason : Addition of $HBr$ on $2-$butene follows Markovnikov rule.