“Was death the consequence of sin, as Scripture seems to say pretty plainly?”
With respect to Adam - yes.
“Or did God use cycles of death to bring about the variety of creatures we see today?”
Yes, but without the “Or” God may have had different plans for mankind than for animals.
“Also, was Adam created with the appearance of age?”
Who knows and why is it even relevant?
So you don’t really believe the biblical account that God literally formed Adam out of dust and then formed Eve out of a rib from Adam’s side? You believe that Adam (and Eve) literally had parents, who presumably weren’t quite fully “human”?
Not trying to play games with you. Just trying to understand your views.