Which process converts olefins into paraffins?

The major product of the reaction of $2-$butene with cold alkaline $KMnO_4$ is:

Write in brief about the preparation of alkene from vicinal dihalide.

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

When $2-$butyne is treated with $H_2/$ Lindlar's catalyst,compound $X$ is produced as the major product and when treated with $Na/liq. NH_3$ it produces $Y$ as the major product. Which of the following statements is correct?

Consider the following sequence of reactions: $CH_3-CH=CH_2$ $\xrightarrow[700\,K]{Cl_2} A$ $\xrightarrow[420\,K, 12\,atm]{Na_2CO_3} B$ $\xrightarrow[(ii) NaOH]{(i) HOCl} C$. Compound $C$ is: