$CH_3-C \equiv C-CH_3$ $\xrightarrow{NaNH_2}$ $X$. What is $X$?

The product obtained in this reaction is:

Propyne on hydration in the presence of $H_2SO_4$ and $HgSO_4$ gives:

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:

The simplest alkyne is represented by which of the following?

$1$-Alkyne and $2$-alkyne can be distinguished by