Propyne on cyclic polymerisation gives

$CH_3CH_2CH_2I$ $\xrightarrow{alc. KOH} A$ $\xrightarrow{Br_2} B$ $\xrightarrow{NaNH_2 / NH_3} C$. In this reaction,$C$ is:

The reaction $R-C \equiv C-R \xrightarrow{H_2 / \text{Lindlar's catalyst}}$ gives the major product as ..............

Acetylene is prepared industrially by passing electric discharge through graphite electrodes in the atmosphere of

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

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