Yes you can shoot 45 Colt and 454 Casull in the 460 barrel. Some guns shoot the shorter cartridges well and others don't. There's only one way to find out. Try it.

Also a word of advise. Shooting the shorter cartridges can cause a build up of copper, lead, and powder fouling in the area where the shorter case does not fill the chamber to the lead/throat area. It's a good idea to clean the chamber thoroughly before firing the longer case. If it's real dirty the longer cartridge will not chamber. If it chambers and is tight from the build up you can have a very high pressure spike from the restriction.