Markovnikov's rule guides the addition of $HBr$ to which of the following compounds?

Addition of $HCl$ to $3,3$-dimethyl-$1$-butene yields two products,one of which has a rearranged carbon skeleton. Among the following carbocations,select the possible intermediates in that reaction:
$1.$ $(CH_3)_3C-C^+H-CH_3$
$2.$ $(CH_3)_3C-CH_2-C^+H_2$
$3.$ $(CH_3)_2C(Cl)-C^+(CH_3)_2$
$4.$ $(CH_3)_2C^+-CH(CH_3)_2$

Identify $Z$ in the following reaction series: $CH_3-CH_2-CH_2-Br$ $\xrightarrow{NaOH(aq.)} (X)$ $\xrightarrow[Heat]{Al_2O_3} (Y)$ $\xrightarrow{HOCl} (Z)$

The correct statement$(s)$ for the following addition reactions is(are):
$(i)$ $trans-but-2-ene \xrightarrow{Br_2/CHCl_3} M \text{ and } N$
(ii) $cis-but-2-ene \xrightarrow{Br_2/CHCl_3} O \text{ and } P$
[$A$] ($M$ and $O$) and ($N$ and $P$) are two pairs of diastereomers
[$B$] Bromination proceeds through trans-addition in both the reactions
[$C$] $O$ and $P$ are identical molecules
[$D$] ($M$ and $O$) and ($N$ and $P$) are two pairs of enantiomers

What is the product formed when $CH_3-CH=CH_2$ is treated with $B_2H_6$ followed by the action of $H_2O_2$?

Which of the following is the most stable alkene?