a. Comparable if not harder (due to size...these programs are much smaller)
b. probably not necessary for acceptance, might be helpful for perspective in performance
c. yes and no... the UCLA and Stern programs take at least significant portions of their coursework (particularly in the first year) in the econ depts. (not sure about haas and penn) but typically don't do as "hardcore" theory topics. More difficult to get jobs in econ depts from these programs, but these programs have good reps.
d. what's a bpp?