After much testing and researching I found the problem that is causing the local Java 8 JRE to run in the Java 6 plugin.

If you navigate to the following folder (depending on how you installed JPortable):

C:\PortableApps\CommonFiles\Java\bin

Select file javacpl.exe (I suggest right click with and "Run as administrator"):

Select Yes on the User Account Control message:

Now the JPortable JRE 6 Update 22 Control Panel should pop up on the screen:

Select the Java tab and the select "View...":

Now you should see the JRE's JPortable is able to access.

This next step is important

You need to untick the box "Enabled" for the Java 8 Update 202 or whatever you have installed then select "OK"

Then select "Apply":

You may get this warning select "OK"

Now when I re-try and run the Java application on the legacy portable Firefox it works fine:

The problem was I didn't know any other version/versions of Java installed on the same PC have there own Java Control Panel setting stored in there own folder - I assumed the latest version of Java would take precidence over all older versions of Java installed on the PC so if you made the change in the Java control panel for Java 8 JRE Update 202 this would push it down to other version of Java - THIS IS NOT THE CASE

I believe you still have to disable legacy portable Firefox from searching the whole PC for addons for this to function.

Sorry for the long winded answer, I hope this helps someone else in the future.

After much testing and researching I found the problem that is causing the local Java 8 JRE to run in the Java 6 plugin.

If you navigate to the following folder (depending on how you installed JPortable):

C:\PortableApps\CommonFiles\Java\bin

Select file javacpl.exe (I suggest right click with and "Run as administrator"):

Select Yes on the User Account Control message:

Now the JPortable JRE 6 Update 22 Control Panel should pop up on the screen:

Select the Java tab and the select "View...":

Now you should see the JRE's JPortable is able to access.

This next step is important

You need to untick the box "Enabled" for the Java 8 Update 202 or whatever you have installed then select "OK"

Then select "Apply":

You may get this warning select "OK"

Now when I re-try and run the Java application on the legacy portable Firefox it works fine:

The problem was I didn't know any other version/versions of Java installed on the same PC have there own Java Control Panel setting stored in there own folder - I assumed the latest version of Java would take precidence over all older versions of Java installed on the PC so if you made the change in the Java control panel for Java 8 JRE Update 202 this would push it down to other version of Java - THIS IS NOT THE CASE

I believe you still have to disable legacy portable Firefox from searching the whole PC for addons for this to function.