Are small molecules liberated during addition polymerization?

Which of the following alkenes is least reactive towards anionic polymerization?

The Ziegler-Natta catalyst is $....$

$A$ raw material used in making $Nylon-6,6$ is

In the production of thermosetting polymers,which substance is used along with methanal?

The polymer $X$ consists of linear molecules and is closely packed. It is prepared in the presence of triethylaluminium and titanium tetrachloride under low pressure. The polymer $X$ is -