What product is obtained when acetylene is passed through dilute sulfuric acid containing $Hg^{2+}$ ions?

When propyne reacts with aqueous $H_2SO_4$ in the presence of $HgSO_4$,the major product is

In the following series of chemical reactions,identify $Z$.
$C_3H_7OH$ $\xrightarrow[160-180\,^{\circ}C]{Conc. H_2SO_4} X$ $\xrightarrow{Br_2} Y$ $\xrightarrow{Excess \ of \ Alc. KOH} Z$

$CH_3COOH$ is reacted with $CH \equiv CH$ in the presence of $Hg^{2+}$,the product is:

Ozonolysis of acetylene $(HC \equiv CH)$ gives:

But$-1-$yne on reaction with dil. $H_2SO_4$ in the presence of $Hg^{2+}$ ions at $333 \ K$ gives: