I've found that Firefox Portable will still use the default Firefox profile location. Meaning it doesn't matter how many copies you make of it, they're all using the same profile on your computer. I found this out when I downloaded Firefox Developer Edition Portable and it wouldn't run while I had Firefox Portable also running, because "the profile was in use."
Tnx. AFAIC, this means FF Portable is -not- portable.
I had not fixed all my FF problems caused by FF 'password importer-exporter';https://addons.mozilla.or
If you want to totally goof up FF, that is the perfect add-on.
All my bookmarks had lost their individual icons, or 'favicons'.
After a little research, I rebooted with a backup HD connected in secondary mode.
Then I navigated through both HDs to this location;
and same spot in the backup HD.
Then I copied the Firefox folder from the backup HD to the same spot in C:, replacing it.
Result; I fixed FF '(not)-Portable', and got back a full set of slightly out-of-date Bookmarks, complete with favicons (a few still missing, but only about 1%), and even got all my Passwords back.
Shut down, unplugged the backup IDE-HD, rebooted, and tidied up with reg, antivirus, and PUP scans.
I suggest Mozilla rename their FF 'portable' version 'Firefox Unportable' (which also makes it all but 'unsupportable').