What is the nature of alcohols in aqueous medium?

Which isomer of $C_4H_9OH$ has the highest boiling point?

The final product $(III)$ is

Ethanol,when reacted with $PCl_5$,gives $A$,$POCl_3$,and $HCl$. $A$ reacts with silver nitrite $(AgNO_2)$ to form $B$ (major product) and $AgCl$. $A$ and $B$ are respectively:

Which of the following alcohols gives white turbidity almost immediately with the Lucas reagent at room temperature?
$(i)$ $n-$Butanol
$(ii)$ $tert-$Butanol
$(iii)$ Benzyl alcohol
$(iv)$ Allyl alcohol

In the following reaction,'$B$' is