Firefox Portable

Hi

Is it possible -without issues- to have a regular installed Firefox instance and a portable Firefox too, on the same Windows instance? tl;dr I want to use Firefox as normal, and that's no issue, but now -that Quantum is so different- I also want to have a pre-Quantum Firefox (56.0.2) available for one specific site with one specific add-on that is no longer supported and is a must for me. (Please don't suggest alternatives, it has to be the final Firefox before Quantum!)

I can only foresee two potential issues;

For recently posted on your site FirefoxPortableESR_52.6.0_Russian.paf.exe Comodo antivirus shows the file is infected with TrojWare.Win32.Backdoor.Tovkater.ID

When opening .html / .url files or running FirefoxPortable.exe again I now get:

Close Firefox | Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window.

My FirefoxPortable.ini reads:

So, this one is funny.
I create a new virtual machine with Windows 10 x64 updated (1709). Then I download the FirefoxPortable_57.0.4_English.paf.exe file and install it right on the desktop.
I enter that folder and create a new text file, rename it as aa.bat. Right click, Edit. And add these four lines:

start C:\Users\kanu\Desktop\FirefoxPortable\FirefoxPortable.exe
pause
start c:\Users\kanu\Desktop\FirefoxPortable\FirefoxPortable.exe
pause

Hello, i've found that in my FirefoxPortable's folder there are duplicated "App" folder and "Other" folder, and these duplicated ones often are named after my email (i.e: App(info@google.com), Other(info@google.com) ).. can anyone please tell me why is that and if i can get rid of one of the duplicates? This happens in many posrtableApps folders as well, such as skype or filezilla. I have my portable apps on box cloud so that i can access them from several PCs. thanks for any help

I tried to install Firefox 52 ESR Portable in order to be able to use the video call feature on Google Hangouts (this feature is officially brokee in later versions and they haven't released a fix for it yet). I've used portable versions of Firefox in the past before with no problem, but this time it's not working.

Let's say I'm trying to download a web page (complete) from The Wall Street Journal with both stock Mozilla Firefox Quantum current (57.0.4) and the PortableApps.com version. Arrive through Twitter, get through the paywall; here's your free WS article: https://twitter.com/GaryPR7/status/950014058404564993

Trying to download the above article produces the results I've just described. Success with stock Firefox, failure with portable Firefox. No add-ons, everything is set to default.

A while ago i tried installing Firefox Portable Development Edition and ever since then I cannot get my standard Firefox Portable to start. It crashes every time. for a time it would crash and ask if i wanted to start in safe mode and then work in safe mode. Now it won't even do that.

I've tried the following all together even:

The portable version of Mozilla Firefox do not work properly. some features not working, I tried with opera that works very well.
However, the non-portable version of Firefox works very well.

I'm using Firefox Portable on Windows 10 and also have one version installed.

When I make D:\files\PortableApps\PortableApps\FirefoxPortable\FirefoxPortable.exe the default program for http etc. I always get a message that already an instance is running if another window is already open.
(If I ignore the message and don't press enter and try to open the link again it is opening in the existing Firefox..)