$A$ bromoalkane is reacted with the sodium salt of an alkyne to obtain $3$-octyne. What are the bromoalkane and the alkyne respectively?

Which of the following reactions gives $H_2C=C=C=CH_2$?

Compound $(X)$ [styrene] is subjected to the following sequence of reactions: $(i)$ $Br_2/CHCl_3$, $(ii)$ $NaNH_2$ (excess), $(iii)$ $CH_3I$, $(iv)$ $H_2, Na/NH_3(l)$, giving Major Product $(Y)$. The molar mass of the major product $(Y)$ formed is . . . . . . $\text{g mol}^{-1}$. (Given molar mass in $\text{g mol}^{-1}$: $C:12, H:1$)

The major products $P$ and $Q$ in the following reactions,respectively,are:
$H_3C-C \equiv C-CH_2CH_3 \xrightarrow{H_2, \text{Lindlar's Catalyst}} P$
$H_3C-C \equiv C-CH_2CH_3 \xrightarrow{Na/\text{liquid } NH_3} Q$

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

The product formed in the above reaction is