What is the product when acetylene reacts with hypochlorous acid?

Acetylene reacts with a $42\% H_2SO_4$ solution containing $1\% HgSO_4$ to give

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

What is $A$?

The compound $X \ (C_5H_8)$ reacts with ammoniacal $AgNO_3$ to give a white precipitate and reacts with excess of $KMnO_4$ to give the acid,$(CH_3)_2CHCOOH$. Therefore,$X$ is:

An unknown compound $(A)$ has a molecular formula $C_4H_6$. When $(A)$ is treated with excess of $Br_2$, a new substance $(B)$ with formula $C_4H_6Br_4$ is formed. $(A)$ forms a white precipitate with ammoniacal silver nitrate solution. $(A)$ may be: