[Potironette]

An answer! Thanks!

For the accelerating downward, I'm pretty sure that when the platform accelerates down, if it is accelerating at gravity, then then a ball is dropped, the ball doesn't fall for the person inside, though it's falling to the person outside at normal speed. If the platform accelerates downward faster than gravity, then the person inside sees the ball floating upwards while the person outside sees it falling normally. If the platform accelerates downwards slower than gravity, then the person inside sees the ball fall slower down, I think, but either way the person outside sees the ball falling normally.

My problem with the accelerating upward is that I can't visualize it from an outsider's point of view. For the accelerating downward platform, it'll be going down no matter what. However, for the upward accelerating platform, the path the ball takes from the outside is confusing '~'.

If the platform accelerates up at the value of gravity(?), then the ball goes up, then hits the ground where it started? I have no clue.
If the acceleration of the platform is up less than gravity, then the ball goes up, then hits the ground lower than where it started?
If the acceleration of the platform is up greater than gravity, then the ball goes up, then hits to ground higher than where it started?

Actually, maybe I shouldn't even think about this since once the ball is dropped during upward acceleration, the ball goes up according to velocity and so it would be extremely complicated to find when it would hit the ground?

Edit: After thinking about it for a while, that answer is really helpful! I forget that I can see the elevator moving up and the ball moving up as it is also falling down from the outside XD