When acetylene is passed through dilute $H_2SO_4$ in the presence of $HgSO_4$,the compound formed is .....

The incorrect statement regarding ethyne is

The final product of the following reaction is .......
$CaO + 3C$ $\xrightarrow{\text{Heat}} A$ $\xrightarrow{H_2O} B$ $\xrightarrow{H_2SO_4, Hg^{2+}} C$

$C_3H_4 + H_2O \xrightarrow[333 \ K]{Hg^{2+} / H^{+}} [X] \rightleftharpoons{\text{Tautomerisation}} Y$
$X$ and $Y$ are respectively

Ethylidene dichloride can be prepared by the reaction of $HCl$ and

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