I posted here as I can see a better section.
Anyway I have seen a guy on you tube say he downloaded the firmware via octoprint so he could compare it!
I cant find anything anywhere about recovering firmware.
I have an ender 3 board that has a perfect firmware for my machine. BUT I dont know how to get at that firmware to reuse it or make sure I get everything complied in a new one.
Well you can download the firmware but it will be a compiled hex file and not what you might think.
I don't know how to dump it with octoprint - just use avrdude.
Here is an example of how to dump it via command line
I guess you can flash it only on the same microprocessor model.
Thanks for that.
Well it was something he said he had done but never explained how he did it. I get the impression it might have been in the terminal section.
I did a new file in Arduino and followed the instructions ok as it compiled after I commented out something to do with arcs so I could have mesh bed levelling instead. but I dont have the hardware to flash the creality Board. SO at present I am stumped. 
I researched how to find the .hex files that is created in the temp folder and tried to use that to flash the new Board
I guess it was M503
Maybe an Arduino or Raspberry Pi?