Which of the followings statements about the given experimental set up is / are incorrect ?

I) It is used to separate a mixture of two or more miscible liquids for which the difference in boiling points is more than 25 k

II) It is used for the separation of different gases from air

III) The beads in fractionating column provide minimum surface area for vapours to cool

IV) It is based on the principle of repeated cooling and condensation of vapours by providing surface for the vapours