What is an alcoholic solution of $KOH$ used for?

Which among the following will have the highest density?

What is the major product of the following reaction?
$CH_2=CH-CH_2-CH(Br)-CH_3 + KOH \xrightarrow[\text{heat}]{\text{alcohol}} \dots$

What is the major product $Z$ in the given reaction sequence?
$(CH_3)_2 C=O \xrightarrow[(2) H_3O^{+}]{\text{(1) } C_2H_5MgBr} X$
$i) SOCl_2$ $\xrightarrow[\Delta]{\text{ii) } CH_3ONa} Y$ $\xrightarrow[\text{Peroxide}]{HBr} Z$

Explain the stereochemistry of $S_{N}2$ reaction with a suitable example.

The product $(C)$ in the following reaction sequence is:
$4-\text{Bromoethylbenzene}$ $\xrightarrow[\Delta]{Br_2} B$ $\xrightarrow{\text{aq. } KOH} C$