What is the range of the number of carbon atoms in alkanes found in paraffin wax?

The alkane which is next to methane in the homologous series can be prepared from which of the following reactions?
$I$. $2 CH_3 Br \xrightarrow[\text{dry ether}]{Na}$
$II$. $CH_3 COOH \xrightarrow[CaO, \Delta]{NaOH}$
$III$. $CH_3 CH=CH_2 \xrightarrow{H_2 / Pt}$
$IV$. $CH_3 CH_2 Br \xrightarrow[H^{+}]{Zn}$
Correct answer is

When a mixture of methane and oxygen is passed over heated molybdenum oxide, the product obtained is ........ .

Different hydrogen atoms in the compound are represented by alphabets:
$CH_3(A)-CH=CH(B)-CH_2(C)-CH_2(D)-CH(E)(CH_3)_2(F)$
Arrange them in decreasing order of reactivity towards free radical substitution.

Iso-octane is mixed with petrol:

The most strained cycloalkane is