Which of the following will be the final product when $C_2H_2$ reacts with $HCl$?

What is Lindlar's catalyst?

Which alkyne will give $3$-ethylhexane on catalytic hydrogenation?

What will be the product of the reaction $CH_3-C \equiv C-CH_2CH_3 \xrightarrow[(2) \text{ Hydrolysis}]{(1) O_3} \, ?$

An unknown compound $X$ is an unsaturated hydrocarbon. It reacts with $HgSO_4$ and $H_2SO_4$ to give compound $(B)$. Compound $(B)$ on oxidation gives compound $(C)$. Compound $(C)$ on reaction with $NaOH$ and soda lime gives methane. Identify $A$ (which is $X$),$B$,and $C$ by providing the chemical reactions.

$[P]$ $\xrightarrow{Br_{2}} C_{2}H_{4}Br_{2}$ $\xrightarrow{NaNH_{2}/NH_{3}} [Q]$
$[Q]$ $\xrightarrow{20 \% H_{2}SO_{4}, Hg^{2+}, \Delta} [R]$ $\xrightarrow{Zn-Hg/HCl} [S]$
The species $[P], [Q], [R]$ and $[S]$ respectively are: