Would a paint stripper brush remove stain and varnish from a door frame?
That wire wheel might help if there are nooks and crannys, like fine detail. But I am afraid what you will need is a lot of elbow grease and sandpaper. Starting with coarse and working down to fine, using steel wool and/or wire bushes for the detail work. Good quality chemical strippers are helpful if you are able to cope with the mess/smell/health hazards.

Wood stains are called that because they stain the wood, by soaking in and penetrating the wood fibers. You may never be able to remove all traces of the stain and bring it back to "original wood". You should be prepared to consider a new stain, maybe a light color near to what your vision of "original" was. This will help cover inevitable areas of imperfection and help blend the door color prior to varnishing.