The general formula of an alkyne is:

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

Which of the following reagents is used to convert a $C \equiv C$ triple bond to a $C=C$ double bond to give the $Cis$ isomer of an alkene?

$CH \equiv CH$ $\xrightarrow[H_2SO_4]{H_2O/Hg^{2+}} X$ $\xrightarrow{LiAlH_4} Y$ $\xrightarrow{P_4/Br_2} Z$. Here $Z$ is

Ethyne on reaction with dil. $H_2SO_4$ and $Hg(II)$ gives:

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