Rivers wouldn't flow to seas and oceans on a sphere.
I have already explained that that claim is BS.
Gravity isn't glue which magically holds the water in place.
Water flows on the real round Earth just like it would on a hypothetical flat Earth.
The only difference is the overall shape.
Spherical gravity would make water seek its own spherical radius through gravity pulling to center of mass
i.e. if there is place, like in a river, where the water is higher, and it can flow along the river to get closer to the centre of mass, it would.
Gravity is not strong enough to cause Earth to become a perfect sphere, or even a perfect ellipsoid.
The ground is strong enough to mostly hold its shape.
Your next picture is yet another blatant lie.
Water levelling itself over Earth's curved surface is observable, measurable, repeatable and testable, just like the radius of Earth.
What isn't is the surface of water magically becoming flat or Earth being flat.
Again, Earth is not a tiny ball sitting on top of a much larger one like your experiment would require.
Again, REers aren't going to admit defeat just because you lie about reality.