Nope, there is not scientific basis for that at all. At best, you may generate some regular gravity in the opposite direction of the earth's (which in itself I find doubtful) but certainly not anti-gravity. Anti gravity would be extremely weird stuff, since it would be the curvature of space time generated due to something with negative mass, since as I told you before "gravity" doesn't really exist (it's the result of us perceiving space time being curved by something with positive mass).

No. A *really* high-mass spinning ring will create an effect called frame-dragging - i.e. the gravitational field will itself be spinning, causing something falling toward the ring to pick up a rotation and spiral in, even if it had been coming in straight. You would need a black hole or a neutron star to cause appreciable frame-dragging, though. This process also changes the shape of the gravitational field, causing it to be weaker along the poles of rotation and stronger at the equator or sides of the object spinning, which might be what you are thinking of.