Why does electrophilic substitution take place at ortho and para positions in haloarenes ?

When does reduction of substance take place in a reaction?

Explain the fact that in aryl ethers (i) the alkoxy group activates the benzene ring towards electrophilic substitution and (ii) it directs the incoming substituents to ortho -and para -positions in benzene ring .

When does oxidation of substance take place in a reaction?

Haloarene is ortho and para directing Explain.

Where does fertilisation take place?

Aryl chlorides and bromides can be easily prepared by electrophilic substitution of arenes with chlorine and bromine respectively in the presence of Lewis acid catalysts. But why does preparation of aryl iodides requires presence of an oxidising agent ?