Is the lift vector reversed during inverted flight? Heard a physics professor say that when an aircraft flies inverted, the wing assumes a significant angle of attack (by pushing the stick forward) to continue to generate the necessary "upward" lift vector to maintain level flight. I'm confused. I thought the lift "vector" is actually reversed and points towards the ground (not upward) during inverted SUSTAINED straight-level flight? What am I missing here? The horizontal stabilizer is basically an inverted airfoil, and its "lift vector" points downwards, giving the airplane tail-down force. How is the wing any different when it's inverted?
This is easiest to understand with a fully symmetrical wing, which indeed are popular with aerobatic aircraft.  The direction of "lift" has nothing to do with sky or ground and everything to do with your angle of attack to the relative wind.

When inverted, you simply (as the professor said) push forward on the stick, which makes the wind strike the "top" of your wing.  Inverted, this does the trick as lift is now towards your floor, but gravity is toward your head.

Right side up, you make the wind strike the bottom of your wing by pulling back on the stick.