What is the monomer unit of Teflon?

Which of the following is a biodegradable synthetic polymer?

What is the monomer unit of neoprene?

The structural formula of benzene is:

What happens when (Give equations also):
$(i)$ Methane reacts with excess of chlorine in the presence of diffused sunlight.
$(ii)$ Ethanol undergoes combustion.
$(iii)$ Ethyl alcohol reacts with acidified potassium dichromate.

Which of the following polymer substances is inert towards environmental processes?