Explain the tetravalency of carbon with the help of electron dot structure.

What happens when:

Methane reacts with excess of chlorine in the presence light.

Also give the chemical reaction involved.

What happens when:

Ethyl alcohol reacts with acidified potassium dichromate.

Also give chemical reactions involved.

The general formula of three compounds $\mathrm{A}, \mathrm{B},$and $\mathrm{C}$ is ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}}$. $\mathrm{B}$ has the highest boiling point and $\mathrm{C}$ has the lowest boiling point.

Mention the type of compound $\mathrm{A}, \mathrm{B}$ and $\mathrm{C}.$