Browser with support for Portable mode, run in fullscreen and UserJS?

Question

Opera

We need the ability to make a portable version of the browser with UserJS preinstalled so that it can be launched immediately in full screen mode.
It is possible to use many tabs is not needed.
The small size of the portable archive is desirable.
Opera
There is a portable mode, UserJS, there is an option -fullscreen.
At startup, it tries to do something (listen on ports?) that causes Windows Firewall to show the "Do you want to allow this program..." window. If you do not allow it, then opera starts and works normally, but this option is not good, you need to start it and open the browser, without extraneous windows.
I disabled the bittorrent client in about:config, and other unnecessary things, but this does not help.
Opera unite is disabled (by default).
Google Chrome
The portableapps version has UserJS.
After shutting down (closing the browser window), the Chrome process remains running: portableapps.com/node/26951 .
The link suggests disabling Google Cloud Print in about: flags, but I don't have that option there. In normal settings, Cloud Print is disabled (by default).
Mozilla Firefox
Version with portableapps .
UserJS is not supported out of the box, so I have not considered it yet.
As it turned out, GM appeared in ff about six years ago, a few months later its support was built into Opera 8, and more recently into Chrome. So we can consider GM as the founder of userscripts.
It's just not clear how to run FF4 in full screen mode.
UPD
There were no extensions that run FF4 in full screen mode.
But it turned out that if you exit firefox in full screen mode (using Alt-F4) before creating a portable archive, then the next time you start it, it will start in full screen mode. This solved the problem.

Answer 1

UserJS is not supported out of the box, so I have not considered it yet.

And why is it "out of the box"?
You can, for example, install greasemonkey on a portable version, clear personal data, transfer it all to another person, and for him it will be “out of the box”.

Answer 2

And what does not suit Mozilla Prism or am I not talking about that?