I would like to revert Firefox to a previous version and keep it that way.
I understand that the developers don't want users doing this.
I have tried simply uninstalling and re-installing the proper version (their instructions here), but when I try to start Firefox afterwards, it prevents me from importing my profile. Firefox does this if the profile is newer than the installed version. In this question, I am asking how to revert and maintain my profile.
I have searched Superuser but don't see an answer. This answer is about old profiles; my question is actually about profiles newer than the installed version. This answer is also about copying an older profile. This answer is about going from 32-bit to 64.