Hydrogen peroxide in its reaction with KIO4 and NH2OH respectively, is acting as:
A reducing agent, an oxidizing agent
Let us look at the reactions one at a time:
NH2OH+H2O2⟶N2O3+H2O
In this reaction, nitrogen is oxidized from (-1) to (+3).
Hence, H2O2 is an oxidizing agent.
In the other case, it reduces iodine from (+7) to (+5):
KIO4+H2O2⟶KIO3+H2O+O2