Which of the following has maximum iron content?

Which statement is incorrect regarding the Hall-Heroult process for the metallurgy of aluminium?
$1$. Use of $Na_3AlF_6$ lowers the melting point of $Al_2O_3$.
$2$. Steel vessel with a lining of carbon acts as the cathode.
$3$. Graphite is used as the anode.
$4$. Carbon dioxide gas is generated at the cathode.

Aluminium is obtained by:

Extraction of metal from the ore cassiterite does not involve:

In the extraction of copper from its sulphide ore,the metal is finally obtained by the reduction of cuprous oxide with

The inner lining of a blast furnace is made of ...........