Calcium carbide on reacting with water gives

$CH_3-C \equiv C-O-CH_3 \xrightarrow{dil. H_2SO_4, HgSO_4} \text{major product}$

What is $A$?

An alkyne has the molecular formula $C_6H_{10}$. The number of $1$-alkyne isomers (excluding stereoisomers) possible for it is

The compound $X$ on reaction with $HgSO_4 + H_2SO_4$ gives $Y$ which on oxidation gives acetic acid. $X$ is

Give the main product of the following reactions:
$(i)$ $1,1,2,2-$tetrabromopropane + zinc powder in methanol.
$(ii)$ Reaction occurring on passing hydrogen gas through carbon electrodes at high temperature in an electric arc.