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Both on and upon are prepositions meaning essentially the same thing.
Upon is merely more formal; however, uses such as "once upon a time," "row upon row," and "the autumn is upon us" are idiomatic and thus the alternative seems unnatural and jarring.
In all your examples, either word would work fine, but you will notice that upon sounds more formal.
With files from the Canadian Oxford Dictionary.
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Knowing that death is certain and that the time of death is uncertain, what's the most important thing?
—Bhikkhuni Pema Chödrön
Humankind cannot bear very much reality.
—From "Burnt Norton," Four Quartets (1936), T. S. Eliot
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