1) Your psp will give an error saying the current firmware is higher than that on the UMD and so wont let you downgrade. Oh the joy if it did.
2) Yes that would be the case, this is what custom firmware is for.
3) If you have the latest firmware (custom or official) you can play any game. It does not have to be that specific firmware.
4) You have official firmware, no homebrew allowed. You can downgrade and luckily for you there is a simple way of doing it.
5) TA-082 is a patched motherboard which blocked some downgraders, not sure if it was intentional by sony but it did.
What you need to do now is:
Upgrade to 2.80 by using this link. The reason i choose this firmware is its the easiest and is compatible if you have a TA-082 motherboard.
Downgrade to 1.50 using this link and looking at the correct section titled 2.80
Upgrade to 3.52 M33-4 this is the custom firmware i was talking about. From here you can upgrade to 3.90 M33 t=which is the latest so your psp will play all games all homebrew and have alot more features.
Hope that helps.
Kev
