Often this sales tactic is used in stores carrying used equipment. They usually offer a trade in credit off for your old lenses, but it will be really low usually, only a hundred of dollars if that. They get more used inventory at dirt cheap prices to sell, and move new product at the same time.
Any EF lense will work on any EOS camera.
EOS 6D, EOS 7Dmk2, EOS M, EOS M3, EF 8-15mm Fisheye F4.0L, EF 17-40mm F4.0L, EF 35mm F2, EF 40mm F2.8, EF 50mm F2.5 Macro, Sigma 50mm F1.4 Art, EF 85mm F1.8, EF 70-200mm F2.8L, EF 2x, EF 1.4x mk2, EF life size converter, EF-M 11-22mm, EF-M 22mm, EF-M 18-55mm, M Mount Rokinon 8mm Fisheye.