Which functional group is present in alcohol?

What is the molecular formula of ethanoic acid (acetic acid)?

Which of the following compounds is an addition polymer?

The class of organic compounds which gives effervescence with $NaHCO_3$ solution is:

Explain the given reactions with examples:
$(a)$ Hydrogenation reaction
$(b)$ Oxidation reaction
$(c)$ Substitution reaction

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.