2016: The oxidizing agent is the species that loses electrons. In this reaction, H2O2 loses two electrons to form H2O. So, H2O2 is the oxidizing agent.
2017: In a redox reaction, oxidation number of an element changes from negative to positive or from positive to negative.
2018: The reducing agent is the species that loses electrons. In this reaction, Fe3+ loses three electrons to form Fe2+. So, Fe3+ is the reducing agent.