So it seems we can swap both the objects and the locations?
Yes.
In your setup, if we take object A and lower it to the altitude of B, then take B and lift it up to the (former) altitude of A, will the object B reach ground first?
Yes, the object B will reach ground first.
Can the objects do anything during their descent, such as opening a parachute at a predetermined altitude? changing their aerodynamics?
Also, can they include sensors and electronics?
Yes.
Yes, the object B will reach ground first.
Can the objects do anything during their descent, such as opening a parachute at a predetermined altitude? changing their aerodynamics?
Also, can they include sensors and electronics?