So, since this is rather complicated, you probably shouldn't do it if you don't know how and I can't really write up a "how to" or guide at the moment. I just wanted to let people who know what they are doing or have time to write up a guide for others, that you can fix the downgrade partition problem with adb parted.
I basically ran the AML USB software with the 0921 firmware -> flashed the fire_TM_factoryromresets.zip
that I posted above -> put TWRP on the sd card and booted into it for adb access -> Then 'adb shell parted -s /dev/block/avnftli mkfs 1 fat32' and in my case did the same to 'mtdblock8'. I used the fdisk.cmd and fdisk.sh from fldc's Crystal Batch 3 recovery package, you can find those in my unbricking thread. Then this to use them:
adb push fdisk.cmd /tmp
adb push fdisk.sh /tmp
adb shell chmod 775 /tmp/fdisk.sh
adb shell /tmp/fdisk.sh
adb shell parted -s /dev/block/avnftli mkfs 1 fat32
adb shell parted -s /dev/block/mtdblock8 mkfs 1 fat32
You might not have to do the 'mtdblock8' you should 'print' all your blocks before you do anything and see where you are at.
That recreated 250:33, which is avnftli1, that was previously missing and fixed those partitions. From there I installed "happy spring festival" but that had some issues, when trying to access settings -> storage it would crash. So I booted into the stock recovery and did a factory reset and wiped the media partition, then I flashed CM10 with the latest comp zip and so far at least everything seems okay. Settings -> storage reports the right allocation for the internal sd card. I'll have to look into it a little further to see if all the partitions appear correct but it looks good to go at the moment and at least the tablet is functional.
EDIT: Also on "avnftli1" set mklabel to "msdos". There is some info on this thread
EDIT2: Looks like TWRP already has fdisk so there is no need to push it or the fdisk.sh to /tmp. You should be able to just use parted to partition those blocks. Works for me and I'm back to normal.
This post has been edited by fuser-invent: 22 March 2013 - 09:14 AM