If somehow there are two different robots parked on the yellow center platform and they are from different alliances, would you split the points or would there be no points awarded?

They could both get points as long as they meet the definition of center parked. There is no limit set to the number in the center.

you can enter 4 robots in the scoring calculator as center parked

I mean, either way, the point differential is the same. The answer is they all get 6 points.