Which of the following organic compounds has the same hybridization as its combustion product $(CO_2)$?

The general formula of an alkyne is:

In the reaction $CH_3-C \equiv C-CH_3 \xrightarrow[(ii) H_2O/Zn]{(i) X} CH_3-CO-CO-CH_3$,what is $X$?

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

Formation of ethylene from acetylene is an example of

The reaction of $2-$pentyne with dilute $H_2SO_4$ and $HgSO_4$ yields...............