Self-reduction process is used in the extraction of $-$

The Ellingham diagram represents a plot of:

In the extraction of $Zn$,which gas is burnt in the jackets surrounding the retorts?

In the $Down's$ process,why is $CaCl_2$ added to $NaCl$?

The 'Hydrometallurgy' process is used for the extraction of which metals?

Observe the following statements:
Statement-$I$: The choice of reducing agent for the reduction of an oxide ore can be predicted by using Ellingham diagram,a plot of $\Delta G^{\ominus}$ vs $T$.
Statement-$II$: According to Ellingham diagram,metal oxide with higher $\Delta G^{\ominus}$ is more stable than the oxide with lower $\Delta G^{\ominus}$.