An unsaturated organic compound,$X$ on reaction with hot,acidified $KMnO_4$ gives succinic acid. What is $X$?

What is the product obtained by the reaction of $1$-butene with $HBr$ in the presence of peroxide?

$2-$methylbut$-2-$ene $\xrightarrow[\text{(ii) } Zn / H_2 O]{\text{(i) } O_3}$ products here are . . . . . . .

Arrange the following according to the increasing order of stability: Propene $(I)$,cis-but-$2$-ene $(II)$,trans-but-$2$-ene $(III)$,$2,3$-dimethylbut-$2$-ene $(IV)$,ethene $(V)$.

Electrophilic addition on a carbon-carbon double bond involves the intermediate formation of a more stable carbocation. This statement is called

The intermediate during the addition of $HCl$ to propene in the presence of peroxide is