Considering the Ellingham diagram,which of the following metals can be used to reduce alumina $(Al_2O_3)$?

Which of the following metals cannot be obtained by auto-reduction of their compounds?

When bauxite powder is mixed with coke and reacted with nitrogen at $2075 \ K$,carbon monoxide and $X$ are formed. What is the gas formed when $X$ is reacted with water?

In the process of extraction of gold,
Roasted gold ore $+ CN^{-} + H_2O \xrightarrow{O_2} [x] + OH^{-}$;
$[x] + Zn \rightarrow [y] + Au$
$[x]$ and $[y]$ are :

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.

Write the chemical reactions involved in the extraction of gold by the cyanide process. Also,explain the role of zinc in this extraction.