Which of the following metals is extracted by the electrolytic reduction method?

Name the metal $M$ which is extracted on the basis of following reactions:
$4M + 8CN^{-} + 2H_2O + O_2 \rightarrow 4[M(CN)_2]^{-} + 4OH^{-}$
$2[M(CN)_2]^{-} + Zn \rightarrow [Zn(CN)_4]^{2-} + 2M$

Explain the hydrometallurgical process with a suitable example.

In the process of leaching of gold by cyanide,what are the complexes $X$ and $Y$ respectively?
$4Au(s) + 8CN^-(aq) + 2H_2O(aq) + O_2(g) \to 4[Au(CN)_2]^-(aq) + 4OH^-(aq)$
$2[Au(CN)_2]^-(aq) + Zn(s) \to [Zn(CN)_4]^{2-}(aq) + 2Au(s)$
$X$ and $Y$ are:

In the extraction of copper from its sulphide ore,the metal is formed by reduction of $Cu_2O$ with

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?