$CH \equiv CH + HBr \to X$,the product $X$ is:

What is the product when $2-$butyne is treated with liquid $NH_3$ in the presence of lithium?

$CH_3-C \equiv C-CH_3 \xrightarrow{\text{Cold } KMnO_4} (A)$
Product $(A)$ is:

The $C - H$ bond length is minimum in the bond formed by

When acetylene is passed into dilute sulphuric acid containing $Hg^{2+}$ ions,the product formed is

Which alkyne yields butanoic acid $(CH_3CH_2CH_2CO_2H)$ as the only organic product on treatment with ozone followed by the hydrolysis?