Extraction of copper from copper pyrites is done by heating in a blast furnace. On which principle is this method based?

The inner layer of a blast furnace is made of:

In the electrolytic extraction of aluminum,molten cryolite $(Na_3AlF_6)$ is used to:

In which of the following pairs of metals are both commercially extracted from their respective ores by the carbon reduction method?

Which form of iron has the highest melting point?

Consider the following metallurgical processes:
$(i)$ Heating impure metal with $CO$ and distilling the resulting volatile carbonyl (boiling point $43\,^{\circ}C$) and finally decomposing at $150\,^{\circ}C$ to $200\,^{\circ}C$ to get the pure metal.
$(ii)$ Heating the sulphide ore in air until a part is converted to oxide and then further heating in the absence of air to let the oxide react with unchanged sulphide.
$(iii)$ Electrolysing the molten electrolyte containing approximately equal amounts of the metal chloride and $CaCl_2$ to obtain the metal.
The processes used for obtaining sodium,nickel and copper are,respectively,