"What happens if we throw the ball forward or backward? Will we again have a fictitious force?" Yes, you will. Only that force will be in the plane of the orbi

"What happens if we throw the ball forward or backward? Will we again have a fictitious force?" Yes, you will. Only that force will be in the plane of the orbit. Throw the ball forward and you raise its orbit - so it will start going forward, end up going "up" and then cycle back down exactly one orbital period later. Throw it backwards and you will lower its orbit. It will go back, down, the up again. Unless you throw it too hard, in which case it will re-enter and burn up.