yes, you can do the QA Flag option once in CFW.
1) First, you need to install the official firmware 4.82 (and only 4.82 !).
2) patch your NAND or NOR (depends your console's chipset version)
3) Once it's patched, you can install a CFW 4.82 (not lower).
4) Once you are on CFW 4.82, you are free to downgrade to another CFW version or keep the one you installed.
if you want to downgrade :
install the
standalone QA Flag program, and launch it to "toggle" and enable that option (it's allows you to downgrade, among other things it unlocks). Once back on XMB after launching qatoggle, shutdown and reboot the console. Then install another CFW from any version.