Identify the alkadiene molecule from the following.

Ozonolysis of $2-$methyl$-2-$butene,in presence of $Zn,$ yields $--$

Which reaction will yield $CH_2 = C = CH_2$?

Which of the following intermediates is formed to produce the major product in the addition of $HBr$ to propene in the presence of peroxide?

Number of structural isomeric alkenes (molecular formula $= C_6H_{12}$) which all give $n$-hexane on hydrogenation in the presence of a metal catalyst.

Arrange the following alkenes in increasing order of their enthalpy of hydrogenation $(-\Delta H)$: