Which of the following gases is poisonous?

$C_3H_6$ $\xrightarrow{X} Y$ $\xrightarrow[C_6H_6]{AlCl_3} Z \text{ (major product)}$
$X$ and $Z$ respectively in the following reaction sequence are

Product $(C)$ is

Which type of reactions are easily performed by alkane and alkene?

Compound $X$ of molecular formula $C_4H_6$ takes up one equivalent of hydrogen in the presence of $Pt$ to form another compound $Y$,which on ozonolysis gives only ethanoic acid. The compound $X$ can be:

$CH_2(COOH)_2 \xrightarrow{P_4O_{10}, \, 150^\circ C} X$
Compound $(X)$ is