rectification; Abhyankar-Sathaye embedding problem; variable coverings of \(\mathbb{P}^ 1\); Galois groups; Hurwitz monodromy group; finite groups; Galois group of regular extension of \(\mathbb{Q}\); universal Frattini cover; rational point on varieties; regular realization problem on dihedral groups; real branch points; totally nonsplit extension; field of totally real numbers; fields of definition; inverse Galois problem; symmetric group; modular curves 