Toilet won't come off the flange
I'm betting that whomever installed it last used an adhesive to secure and seal the toilet to the closet flange and/or the floor. It sounds as if you are renovating so unless the toilet has value (or fond memories) break it out with long handled sledge hammers (use eye protection). The time saved by not solving a mad scientist monstrosity might be worth the cost of a mid-priced new toilet.