Conjugated double bond is present in

Addition of $HCl$ to vinyl chloride $(CH_2=CHCl)$ gives $1, 1-$dichloroethane $(CH_3-CHCl_2)$ because of:

The number of alkene isomers with the molecular formula $C_4H_8$ is ....

Arrange $HI$,$HCl$,$HBr$,and $HF$ in increasing order of rate of reaction with alkene.

The reaction of $1,3$-butadiene with $1$ equivalent of $HBr$ at different temperatures yields products $A$ and $B$. Identify the relationship between $A$ and $B$. The reaction scheme is as follows:
$CH_2=CH-CH=CH_2 + HBr (1 \text{ eq}) \xrightarrow{25^{\circ}C} A$
$CH_2=CH-CH=CH_2 + HBr (1 \text{ eq}) \xrightarrow{-80^{\circ}C} B$

For the reaction $CH_3-CH=CH_2 + HOCl \to A$,the product $A$ is: