Which one of the following oxides is reduced by water gas to obtain the metal during its extraction?

The reactions which occur in a blast furnace at $500-800 \ K$ during the extraction of iron from haematite are:
$(i)$ $3 Fe_2O_3 + CO \rightarrow 2 Fe_3O_4 + CO_2$
$(ii)$ $Fe_2O_3 + 3 C \rightarrow 2 Fe + 3 CO$
$(iii)$ $Fe_3O_4 + 4 CO \rightarrow 3 Fe + 4 CO_2$
$(iv)$ $Fe_2O_3 + CO \rightarrow 2 FeO + CO_2$

Which of the following pair of metals are extracted by self-reduction from their main ores but do not evolve $H_2$ gas with dilute $H_2SO_4$?

The electrolytic reduction of alumina to aluminum is made possible by the Hall-$H$éroult process in the presence of:

Which oxide will not give metal on heating?

Explain the extraction/purification of copper.