Using a Second (or Third) Profile with Firefox Portable
In the support you say "Note that only one profile can be used at a time, even with MultipleInstances turned on in the advanced launcher INI. This is a limitation of Firefox itself."
But i can tell you that multy profiles can be used simultaneously when firefox.exe is started with -no-remote parameter. So you need to fix FirefoxPortable.exe and FirefoxPortable2ndProfile.exe to use "firefox.exe -no-remote".