QA Flag Questions (may be nooby)

hello so i just recently downgraded my ps3 to 3.55 :D and i have a few questions about QA flag

so i used this thread: http://www.ps3hax.net/showthread.php?t=33989

i used method one and was required to toggle QA flag

heres my questions, sorry if they are nooby :p

1. does QA Flag stay enabled when you go back to OFW

2. if i update to 4.40 OFW and QA flag is still enabled, can i downgrade without my flasher?

3. how do you turn off QA flag?

4. will anything bad happen if i play BO2 on OFW with QA flag on?

5. what are the differences between a QA flag toggled console and one that is not?

thanks, and another thanks to the poeple who helped me downgrade and unbrick :D