There are two non-Euclidean geometries: hyperbolic geometry and ellptic geometry.
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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.
Hyperbolic, elliptic, projective are three possible answers.
Yes. (The answer may be complicated somewhat in non-Euclidean geometries, but it's possible in Euclidean geometry if the lines are parallel).
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.
No, both spherical and hyperbolic geometries are noneuclidian.