It is covered well in other questions that sacrificing one creature cannot fulfill the requirements for two abilities that are both activated abilities (have 'Sacrifice a creature: do something', like Falkenrath Aristocrat), or other costs ("As an additional cost to cast Altar's Reap, sacrifice a creature"), but can cause multiple triggered abilities (like Zulaport Cutthroat's).
However, there's one other type of sacrifice that some cards call for; when you're commanded to ("Target opponent sacrifices a creature" as in Cruel Edict), or optionally "may sacrifice" (like Brain Gorger).
Are those "commanded to" or "optionally may" actions costs (and therefore must have a creature sacrificed specifically to it and no other cost), or some other sort of trigger?
A complete example: I have a Falkenrath Aristocrat and a Bane Alley Blackguard in play. An opponent casts Cruel Edict on me. Can I sacrifice the Bane Alley Blackguard to the Falkenrath Aristocrat's ability (she gains indestructable for the turn and a +1/+1 token), and have fulfilled the requirements for what Cruel Edict needs me to do?