'''Firefox does not support downgrades, even though this may have worked in past versions. If you install Firefox Nightly and later downgrade to an earlier version, you may experience issues with Firefox if they share the same profile of data.'''
'''Until we support dedicated profiles per channel in the installer [https://bugzilla.mozilla.org/show_bug.cgi?id=1373244 Bug 1373244], so as to use Firefox Nightly alongside another version of Firefox such as Beta, Release or ESR you need to create and use a separate profile for NightyNightly!'''