I am in the process of remodeling my basement bathroom. When I removed the existing toilet and wax ring the flange seems to be cemented to the floor as well as the pipe. The bolts are rusted and I cannot remove them. What should I do? Should I try to break off the existing flange?

You did not say why you are trying to remove the flange. It sounds like it is OK as is to reuse if you are just replacing the toilet. Buy a high quality wax replacement ring. One thing to keep in mind. If you raise the floor because new flooring or the like, you can buy a deeper/thicker wax ring made for this situation.

I would attempt to remove the bolts and save the flange. See if you can tap them down to where they will slip out of the slots and replace them with new ones. Good luck, Tom