In the extraction of which of the following metals is a complex salt formed?

In the electrolysis of alumina $(Al_2O_3)$,cryolite $(Na_3AlF_6)$ is added to:

Heating a mixture of $Cu_2O$ and $Cu_2S$ will give:

The main reactions occurring in a blast furnace during the extraction of iron from haematite are $....$.
$(i)$ $Fe_2O_3 + 3CO \to 2Fe + 3CO_2$
$(ii)$ $FeO + SiO_2 \to FeSiO_3$
$(iii)$ $Fe_2O_3 + 3C \to 2Fe + 3CO$
$(iv)$ $CaO + SiO_2 \to CaSiO_3$

Which metals are extracted using the self-reduction method?

In the electrolytic reduction of alumina,why is cryolite $(Na_3AlF_6)$ primarily added?