Assumed common descent, but fair point. Why can't a trait one's great ancestors had be acquired by one's descendents? If man changed to a cockroach -- arguably something much more capable of surviving calamties -- would that be evolving to a superior creature.
Not the same problem. That's inheritance down the tree, not up. That "mamms on a T. rex" thing you clammed up on: the point was that things don't move down the tree or from branch to branch. The wrong line of reptiles, one that split off from dinos before dinos were dinos, was the one that grew the mammaries and started moving toward hair, live birth, etc.
That's why evolution says there are things that should not be found. Three ear bones in a salamander. Human bones down among the trilobites. Lots of things, but it's getting pretty late for them to turn up.