What is formed when acetylene reacts with alkaline $KMnO_4$?

Which of the following is(are) example$(s)$ of nucleophilic addition reaction in the case of acetylene?

An unknown compound $A$ has a molecular formula $C_4H_6$. When $A$ is treated with an 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

Identify $Z$ in the following series of reaction:
$CH_3-CH_2-OH$ $\xrightarrow[170^{\circ} C]{conc. H_2SO_4} X$ $\xrightarrow[CCl_4]{Br_2} Y$ $\xrightarrow[\Delta]{alc. KOH} Z$

Which of the following is a homologue of ethyne?

Identify the alkyne formed by the reaction of calcium carbide with water.