An alcoholic solution of $KOH$ is a specific reagent for which of the following reactions?

$2$-chlorobutane $+ Cl_2 \rightarrow C_4H_8Cl_2$ (isomers)
Total number of optically active isomers shown by $C_4H_8Cl_2$,obtained in the above reaction is......................

The following reaction is described as:
$CH_3(CH_2)_5-CH(CH_3)-Br + OH^- \rightarrow HO-CH(CH_3)(CH_2)_5CH_3 + Br^-$

What is the correct order of leaving group ability for the following groups?
$I. -OAc$
$II. -OMe$
$III. -OSO_2Me$
$IV. -OSO_2CF_3$

The major product of the following reaction is:
(Structure of $4-$bromo-pent$-2-$en$-2-$amine derivative) $\xrightarrow[{S_N2}]{{KOH}}$

Why is the solubility of haloalkanes in water very low?