$CH_2=CH-CH_3 + HBr \to ?$ What will be the product formed?

For the given reaction sequence,identify $C$ and $D$:
$3\text{-methylbut-1-ene}$ $\xrightarrow[(ii) NaBH_4]{(i) Hg(OAc)_2/H_2O} A$ $\xrightarrow{H^\oplus/\Delta} B$ $\xrightarrow{O_3/Zn/H_2O} C + D$

Alkene $X$ $\xrightarrow[\Delta]{KMnO_4}$ (Butan$-2-$one) $+$ (Pentanoic acid). $X$ is

The following reaction was carried out.
The final product formed in the above reaction sequence is

Compound $X$ on reaction with $O_{3}$ followed by $Zn/H_{2}O$ gives formaldehyde and $2-$methylpropanal as products. The compound $X$ is :

Which of the following intermediates is formed to produce the major product in the addition of $HBr$ to propene in the presence of peroxide?