Which of the following is the most stable alkene?

Write the mechanism of hydration of ethene to yield ethanol.

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

The reaction of $1-$ethylcyclopentene with $BH_3 / THF$ followed by treatment with $H_2O_2 / NaOH$ produces:

An alkene $X$ with formula $C_4H_8$ does not exhibit geometrical isomerism. In the conversion of $X$ to $Y$,the correct sequence of reagents $A$ and $B$ used are ($Y$ gives iodoform test):
$X$ $\xrightarrow{A} \text{Intermediate}$ $\xrightarrow{B} Y$

Arrange the following compounds in the decreasing order of their reactivity towards electrophilic addition of $HBr$:
$(a)$ $CH_3-C(CH_3)=CH_2$
$(b)$ $CH_3O-C(CH_3)=CH_2$
$(c)$ $CH_3OCH_2-C(CH_3)=CH_2$