A320M-HDV R4.0 upgrade bios

I would contact ASRock tech support to inquire:
http://event.asrock.com/tsd.asp

They will be able to answer your questions better than I can. I don't see any restriction
on updating using the 2400g but I am not 100% certain. As for the update order,
I suspect the system won't allow you to flash to 7.00 if there is a required
version in between. At that point you just need to download all the BIOS versions
between your current one and 7.00 and update to the most recent one it allows
until it allows you to update to 7.00.

In other words:
You have versions 3.70 and 4.00 on your flash drive.
If when you go to the instant flash option in the BIOS it shows both then update
to the newest version it shows.

Repeat until you can update to 7.00.

ASRock should be able to answer that for you too however.

Good luck with the upgrade

If you are not upgrading your CPU and your system is stable, don't update. There
will be no benefit to 7.00 for you.