(a) "Employment" defined; generally; exceptions. As used in this act, "employment" means service: (i) Performed by an employee defined under 26 U.S.C. § 3306(i) including service in interstate commerce, except 26 U.S.C. § 3121(d)(2) does not apply; (ii) Subject to any federal tax against which credit may be taken for contribution payments into any state unemployment fund; (iii) Required to be employment under this act as a condition for full tax credit against the tax imposed by 26 U.S.C. §§ 3301 through 3311; and (iv) Otherwise specified under W.S. 27-3-104 through