Please clarify when to use 'depending upon' and 'depending on'? Also, how do they differ from 'depend upon' and 'depend on'?
They are interchangeable and synonymous, with upon only slightly more formal.
I would use "depending on" or "dependent upon."
While, theoretically, no combination is incorrect when spoken or written, "depending upon" is too informal for the latter. Use "dependent upon," instead.