Only way to make a flash backup without CFW is through any type of flash reader/writer (E3/Teensy/Progskeet with assorted clips - is needed for anything over 3.55 OFW anyways since you have to byte-reverse the dump to write back)
You can dump NOR/NAND from any CFW at this point using MM.
No to the latter question, though you can always run it through a dump checker. Takes all of a minute once on CFW. (the only hashes that will fail are ROS hashes but it's all good - the important thing is flashing back the same CFW you had prior)
The reason it's more difficult when dumping on OFW is because you're effectively making a backup of your system in working condition. If your clip is off, or wired incorrectly, you can get a bad dump, and then after byte-reversing it and flashing it back, you have a brick. If your original dump was bad, then you have a doorstop. It's why most people recommend reading the flash several times to confirm the MD5/SHA1 are the same across dumps, and then to store said dumps in multiple places.
For the too long didn't read crowd:
1. Have someone downgrade or properly downgrade your unit to 3.55 OFW.
2. Install Rebug 4.76.1 (w/e latest is) from XMB.
3. Install Rebug Toolbox from install packages.
4. Launch Rebug Toolbox, go to last column and choose dump flash to file. Stick USB in right most USB port
5. Profit.
