Which of the following catalysts is used in the polymerization of $CH \equiv CH$ to $C_6H_6$?

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

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

Which of the following is the most acidic substance?

The hydrocarbon which can react with sodium in liquid ammonia is

Identify the alkyne in the following sequence of reactions:
Alkyne $\xrightarrow{\text{H}_2, \text{Lindlar's catalyst}} A$ $\xrightarrow{\text{Ozonolysis}} B \text{ (only)}$
Given that $B$ is obtained from $\text{CH}_2=\text{CH}_2$ via the Wacker process.