$A$ hydrocarbon $X$ with molecular formula $C_4H_6$ decolourises bromine water and forms a white precipitate in ethanolic $AgNO_3$ solution. Treatment of $X$ with $HgCl_2$ in aqueous $H_2SO_4$ produces a compound,which gives a yellow precipitate when treated with $I_2$ and $NaOH$. The structure of $X$ is

$CH_3-CH_2-CH_2-C \equiv CH \xrightarrow[\text{Excess}]{HCl} ?$

Consider the following transformations of a compound $P$ $(C_9H_{12})$:
$(i)$ $P \xrightarrow{NaNH_2, C_6H_5COCH_3, H_3O^+/\Delta} R$ (Optically active)
(ii) $P \xrightarrow{Pt/H_2} \text{propylcyclohexane}$
(iii) $P \xrightarrow{X, KMnO_4/H_2SO_4/\Delta} Q$ ($C_8H_{12}O_6$,Optically active acid)
Choose the correct option$(s)$:
$(A)$ $P$ is $3-$cyclohexylprop$-1-$yne
$(B)$ $X$ is $Pd-C/\text{quinoline}/H_2$
$(C)$ $P$ is $1-$cyclohexylprop$-2-$yne
$(D)$ $R$ is $1-$cyclohexyl$-4-$phenylbut$-3-$yn$-2-$ol

An alkyne has the molecular formula $C_6H_{10}$. The number of $1$-alkyne isomers (excluding stereoisomers) possible for it is

Which of the following gives propyne on hydrolysis?

Write the following reactions:
$1$. Complete combustion of ethyne in the presence of air.
$2$. Reaction of propyne with alkaline $KMnO_4$.