Octane number has $0$ value for

What is the correct order of ease of replacement of the hydrogen atom by a chlorine atom in the following compound by photochlorination?

On treating a mixture of two alkyl halides with sodium metal in dry ether,$2-$methylpropane was obtained. The alkyl halides are

Given below are two statements:
Statement $I$ : The boiling point of three isomeric pentanes follows the order
$n$-pentane $>$ isopentane $>$ neopentane
Statement $II$ : When branching increases,the molecule attains a shape of sphere. This results in smaller surface area for contact,due to which the intermolecular forces between the spherical molecules are weak,thereby lowering the boiling point.
In the light of the above statements,choose the most appropriate answer from the options given below:

Complete the following reactions:
$(i)$ Liberation of dihydrogen gas from methane.
(ii) Oxidation of $2$-methylpropane.

Which of the following does not represent the correct major product?