When acetylene reacts with $HCl$ in the presence of $HgCl_2$,the product is

$But-2-yne$ and hydrogen (one mole each) are separately treated with $(i)$ $Pd / C$ and $(ii)$ $Na / \text{liq. } NH_3$ to give the products $X$ and $Y$ respectively. Identify the incorrect statements.
$A$. $X$ and $Y$ are stereoisomers.
$B$. Dipole moment of $X$ is zero.
$C$. Boiling point of $X$ is higher than $Y$.
$D$. $X$ and $Y$ react with $O_3 / Zn + H_2O$ to give different products.
Choose the correct answer from the options given below:

Identify the structures of $P$ and $Q$ in the following reaction sequence:

Which of the following is suitable for the preparation of alkene from alkyne?

The poisonous gas 'Lewisite' is obtained by the reaction of:

Which of the following will produce a chiral molecule after treatment with $H_2$/Lindlar's catalyst?