Sadly some dlc become invalid, unless you resign it. some dlc just works. so i guess its hit and miss, or there is some other factor that i'm unaware of, you better off waiting for another answer about this because there is bound to be someone who actually has this worked out.
Toggle QA is for use on downgraded consoles , so that you can install other Fw safely (less brick risk). its usually used by people who have downgraded consoles using a hardware flasher. recently thanks to all the 4.xxcfw a lot of people are trying these out and therefore having to return to 3.55 before reupdating back to a 4.xx
Toggle Qa allows us to do that more safely as it stops the console realizing its been downgraded. someone with more technical knowledge can explain this in a technical way if you really need it in more depth. that was just a simplified explanation of Toggle QA.
i'd advise you to read the link posted by Vorlone.