Devices shipped with later gingerbread hboots don't boot properly when downgrading to the Froyo hboots. It can take up to 1/2 hour for a normal boot, and flashing RUUs generally fails. We first noticed this on Inspires. Note: This problem only seems to be occurring on devices SHIPPED with GB, not on any of those upgraded to GB.
You can fix if you can temproot, gfree to cycle emmc (even if you can't s-off yet) and dd a current hboot back to the phone. It's a pain in the ass, and I've seen a lot of them - now on some original DHDs and not just Inspires. We've been fixing hboots from downgrades from virtually every older method, including my own.
Since then, we've not done full downgrades - I flash the signed firmware.zip from a very early OTA. This downgrades radio, boot and recovery only - no hboot.
upon reboot:
- There is usb debugging support working
- There is no video support for current GB roms - this is okay - we fix that later
- The GB rom combined with the early froyo kernel will not allow gfree to set s-off, but it will allow emmc cycling, so I flash cwm with an early version kernel.
- Reboot to recovery, and from there, mount system and data, run gfree to set s-off, supercid and sim unlock.
- Once that's done, push a proper boot image, root files and correct wifi module back to the phone - again from recovery.
Here's the firmware.zip I have been using - no HBOOT - fortunately.
http://tau.shadowchild.nl:/files/firmware.zip
So the GB ROM is never downgraded with an HBOOT that can do harm, gfree has done it's thing successfully, and no data is lost on most runs.
Sense 3 changes the picture entirely, as the downgrade firmware is incompatible. Those ROMS must be downgraded. But instead of going to Froyo for those shipped with GB, I strongly recommend downgrading to a 2.x Sense version of GB to avoid those booting issues.
I do not know WHY the newer devices don't work correctly with older hboots, but they don't. I suspect it's some firmware hook not impacted when we flash RUUs.
The WWE 2.50.405.2 RUU is perfectly rootable/s-off-able with the right custom recovery and the above firmware package. It's a popular build, so if we are using goldcard anyway, it's safest to just have everyone downgrade to that, or a comparable GB RUU supporting their own CID.