Which of the following reactions requires an oxidising agent?

When benzyl alcohol is oxidised with $KMnO_4$,the product obtained is

$CH_3 CH_2 OH \underset{\text{step-}1}{\stackrel{Cl_2}{\longrightarrow}} CH_3 CHO$ $\underset{\text{step-}2}{\stackrel{3 Cl_2}{\longrightarrow}} Cl_3 CCHO$
In the above reactions,the role of $Cl_2$ in step-$1$ and step-$2$ respectively is:

The major product in the following reaction is:

In the esterification reaction of alcohols,which of the following occurs?

Which of these dehydrates most easily?