Which oxide will not give metal on heating?

$Ni$ anode is used in the electrolytic extraction of

Given below are two statements.
Statement $I$: According to the Ellingham diagram,any metal oxide with higher $\Delta G^{\circ}$ is more stable than the one with lower $\Delta G^{\circ}$.
Statement $II$: The metal involved in the formation of oxide placed lower in the Ellingham diagram can reduce the oxide of a metal placed higher in the diagram.
In the light of the above statements,choose the correct answer from the options given below.

Cryolite $(Na_3AlF_6)$ helps in:

The order of stability of metal oxides is:

What is the role of the graphite rod in the electrometallurgy of aluminium?