I would to ask for additional info using the comment, but I can not post comments on StackExchange Network yet. Because of being a newbie and not having enough reputation points.
I currently run Linux, but I met such behaviour in the past, no matter of operating system used.
How do you start Firefox instances? Do you use original shortcuts in Start menu / Desktop / Quicklaunch? If yes, you should create the new shortcuts (on the Desktop) with different parameters. Just tell me how do you start Firefox and if you ever edited the parameters for the shortcuts, I will try to find out and write more.
You might also copy-n-paste the content of the profiles.ini file that Firefox uses, this would be helpful. It should be somewhere in the %APPDATA%\Mozilla\Firefox folder or similar.
EDIT 1:
EDIT 2:
OK, you're starting Firefoxes the correct way.
1) The parameter -no-remote should be actually in your devel profile target, so add the -no-remote to the target of the shortcut you're actually using to launch your devel Firefox. Remove the -no-remote parameter from the browsing profile.
2) Check your profiles.ini file as mentioned above. It should contain following lines at the very beginning of the file:
[General] StartWithLastProfile=0 [Profile0] ... file continues... If it does not contain the first two lines, backup the profiles.ini and add the lines. Or change the StartWithLastProfile value from 1 to 0.
After editing the shortcuts and the profiles.ini file, the expected behaviour is:
a) if you click the link from any other application and the Firefox browsing is already running, it should be opened in the browsing profile.
b) if you click the link from any other application and the Firefox browsing is not running, the profile manager should be launched. You will select the browsing profile from the dialog, do not check any of the checkboxes and confirm. The link should be opened in the Firefox browsing profile.
It works for me on Linux and as far as I remember, it also worked for me on Windows in the past.