(i) F exhibits only negative oxidation state because it is the most electronegative element.
(ii) Cs exhibits only positive oxidation state because it is the most electropositive element.
(iii) I exhibits both positive and negative oxidation states. Iodine exhibits — 1, 0, +1, 3, + 5 and + 7 oxidation states (+ 3, + 5 and + 7 oxidation states are exhibited by I due to the presence of vacant d-orbitals).
(iv) Ne is an inert gas, so it neither exhibits negative nor positive oxidation states.