Which of the following oxides cannot act as a reducing agent?

Consider the reaction $H_2SO_{3(aq)} + Sn^{4+}_{(aq)} + H_2O_{(l)} \to Sn^{2+}_{(aq)} + HSO_4^-(aq) + 3H^{+}_{(aq)}$. Which of the following statements is correct?

Consider the following reaction:
$BrCH_2CH_2F + SbF_5 \xrightarrow{SO_2, -60^{\circ}C} CH_2-CH_2-Br^+ + SbF_6^-$
In this reaction,$SbF_5$ acts as:

Which of the following species acts as the strongest oxidising 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 anions would decolourise acidified $KMnO_4$ solution?