What is the number of tertiary carbon atoms in a molecule of isobutane?

Which reactive intermediate is involved in the following reaction?
$2-\text{methylbutane} \xrightarrow{Br_2, hv} 2-\text{bromo}-3-\text{methylbutane}$ (not the major product)

What are $X$ and $Y$ respectively in the following reaction sequence?
Isopentane $\xrightarrow{KMnO_4} X$ $\xrightarrow{\text{dehydration}} \underset{\text{Major}}{Y}$

For the fastest rate of reaction in the given free radical halogenation of cyclohexane,$X_2$ must be:

$(A) + Cl_2 \xrightarrow{hv} \text{monochloro product}$. To maximize the yield of the monochloro product in the above reaction:

Identify the major product of the following reaction: $CH_3-CH(CH_3)-CH_2-COOH \xrightarrow{NaOH + CaO, \Delta}$