Which reaction converts $2$-hexyne into $trans$-$2$-hexene?

The hydration of propyne results in the formation of:

An unknown compound $X$ is an unsaturated hydrocarbon. It reacts with $HgSO_4$ and $H_2SO_4$ to give compound $(B)$. Compound $(B)$ on oxidation gives compound $(C)$. Compound $(C)$ on reaction with $NaOH$ and soda lime gives methane. Identify $A$ (which is $X$),$B$,and $C$ by providing the chemical reactions.

Describe the physical properties of alkynes.

$CH_3-CH(CH_3)-C \equiv CH \xrightarrow{excess \ HBr}$
The product of the above reaction is

Metallic sodium does not react normally with: