Which of the following elements never acts as a reducing agent?

Which of the following acts as an oxidizing agent?

Sulphur dioxide and hydrogen peroxide can act as both oxidizing and reducing agents in their reactions,while ozone and nitric acid act only as oxidants. Why?

Which of the following can act both as an oxidising as well as reducing agent?

Identify the reducing agent in the following chemical equations:
$4Ag(s) + 8CN^{-}(aq) + 2H_{2}O(aq) + O_{2}(g) \rightarrow 4[Ag(CN)_{2}]^{-}(aq) + 4OH^{-}(aq)$
$2[Ag(CN)_{2}]^{-}(aq) + Zn(s) \rightarrow [Zn(CN)_{4}]^{2-}(aq) + 2Ag(s)$

The oxidant which is used as an antiseptic is: