NetBeans 8.2 Won't Run/Open on Mac all of sudd

I was in the middle of coding a project in Netbeans v8.2 and all of a sudden it closed down. When I re-opened it I seen the attached screen.I can't open any projects even though I can see them there, and most options are now greyed out. PLEASE anyone help. I run MAC OS. Please can someone tell me how on earth I revert back to an old version?

NetBeans Info Screenshot of now Netbeans

You don't need to revert back to an old version of NetBeans. Your screenshot shows that NetBeans is incorrectly configured to use Java 11.0.1, but your version of NetBeans (8.2) does not support any version of Java greater than 1.8.

To resolve the issue you must reconfigure NetBeans 8.2 to use JDK 1.8:

Close NetBeans.
Install JDK 1.8 if it is not already installed. (You don't need to remove JDK 11.)
Locate the file netbeans.conf, which resides in the etc directory directly under your NetBeans installation directory.
Open netbeans.conf in a text editor, and locate the line containing the property value netbeans_jdkhome.
The line may be commented out with a leading #. If so, uncomment the line by removing that leading # symbol. Then set the value of that property to specify the actual path to your installed version of JDK 1.8 so that the line looks similar to this:

netbeans_jdkhome="/mypath/to/jdk8"
Save your changes and start NetBeans.

If you still have problems, one further thing you could try is to delete your user directory and cache directory:

Close NetBeans.
Locate and delete your User directory and Cache directory. Their paths are shown near the bottom of the NetBeans Info screen shot posted with your question.
Start NetBeans.

If you still have problems after doing all that then update your post with:

The symptoms of the new issue.
An updated Help > About screen shot.
Any relevant issues in the NetBeans log (View > IDE Log).

One related point regarding NetBeans support for different JDK versions:

As mentioned above, NetBeans 8.2 does not support any JDK > 8.
Apache NetBeans 9.0, the latest release, additionally supports JDK 9 and JDK 10.
Apache NetBeans 10, which will be available soon, will also support JDK 11.