Which compound is a possible product from the addition of $Br_2$ to $but-1-ene$?

Which of the following is the most stable alkene?

Major product of the given reaction is $CH_2=CH-CH_2-I \xrightarrow[CCl_4]{HI(excess)}$

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

The volume of dihydrogen required for complete hydrogenation of $0.5 \ dm^{3}$ of ethene at $\text{S.T.P.}$ is (in $dm^{3}$)

When $2-$butyne is treated with $H_2/$ Lindlar's catalyst,compound $X$ is produced as the major product and when treated with $Na/liq. NH_3$ it produces $Y$ as the major product. Which of the following statements is correct?