Which halogen does not show variable oxidation state?

Which of the following elements exhibits the most basic character?

When $I_2$ is passed through $KCl$,$KF$,and $KBr$ solutions,what happens?

The products obtained when chlorine gas reacts with cold and dilute aqueous $NaOH$ are:

Sulphur dioxide on reaction with chlorine in the presence of charcoal gives compound $(A)$. This on reaction with white phosphorus gives $SO_2$ and compound $(B)$. The correct statement about '$B$' is

Chlorine cannot displace which of the following?