Ellingham Diagram

Which of the following statements about Ellingham diagram are true? i) Ellingham diagram normally consists of plots of Delta_(f)G^(@) Vs T for formation of oxides of elements (ii) Each plot will be straight lines at all temperatures iii) There is a point in a curve below which DeltaG is -ve and above this point the oxide decompose its own iv) Ellingham diagram is restricted to metal oxides v) Ellingham diagram does not say about kinetics of the reduction process vi) Ellingham diagram presumes that the reactants and products are in equilibrium