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There are two non-Euclidean geometries: hyperbolic geometry and ellptic geometry.
No, both spherical and hyperbolic geometries are noneuclidian.
No. Spherical geometry did not disprove Euclidean geometry but demonstrated that more than one geometries were possible. Different circumstances required different geometries. Similarly hyperbolic geometry did not disprove either of the others.
Pi is only constant in Euclidean Geometry, it is not the same in other Geometries. In the non-Euclidean geometry that Relativity theory uses the difference between PiE and PiNE is extremely small, approaching zero.
In some non-Euclidean geometries the 3 angles of a triange will add up to less than 180 degrees. In other non-Euclidean geometries they will add up to more than 180 degrees.