What product is obtained by the oxymercuration of $1$-butyne using $HgSO_4 + H_2SO_4$?

Product $(C)$ is: $Ph-CH=CH_2$ $\xrightarrow[CCl_4]{Br_2} (A)$ $\xrightarrow[(ii) NaNH_2]{(i) alc. KOH} (B)$ $\xrightarrow[(ii) CH_3-Cl]{(i) NaNH_2} (C)$

What will be obtained by the reaction of calcium carbide with heavy water? Give its chemical equation.

What is the type and number of bonds between carbon atoms in calcium carbide?

In the given reaction $x$ is:
$CH_3 - C \equiv CH$ $\xrightarrow{Excess\ HCl} (A)$ $\xrightarrow{H_2O/OH^{-}} (x)$

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.