To stop firefox updating
Tools / Options / Advanced / Updates ......... And check the "Never check for updates "
Download the archived version of Flash you wish to try, and once you've deleted all traces of the existing one , double click the one you've downloaded
FLASH 10.3 HERE
To stop Flash from updating, on your PC go to START / Control Panel / find the flash install and open it, then once again, goto Advance and disable auto updates .
Hope this helps.