[Asus  Eee Pad Transformer Prime] forcemaker:
Hi! (I know that this is an old post, but as newbies gonna search for these answers, I will provide them.)

NVFlash

is a part of the nVidia Tegra SoC (System on Chip) and it

is not stored

in the flash part of your device.

It is (as someone explained) a substantial part of the hardware. It

cannot be removed, disabled, changed or modified

in any known way (well, you could try to solder the chip and do stuff...).

Every(?) Tegra device

has a

unique encryption key

which is part of that code and therefor cannot be altered, too.

There is (again, as I

have been

explained)

nothing you can do with adb, fastboot and APX/wheelie/nvflash that will alter that features

. It is unbrickable, as long as there is no hardware error/defect (e.g. USB port malfunction).

Therefor, flashing any recovery/bootloader/ROM will not remove nvflash abilities.

But beware

: nvflash

has to be used the first time

to create the backup files

before

you go to any ASUS Stock ROM with Android 4.1/4.2 (as my device is a TF300T/TF300TG I

cannot

advice you

on the right version numbers

as they differ from model to model). You must keep the files safe.

They are unique to each device

because of the above mentioned

encryption key

.

You cannot "borrow"

the blob.bin files etc

from any other device

as they are device specific encrypted.

(Often the terminus used is "to install nvflash" which is technically quite wrong as you do not permanently install anything to your device. What you do is to download/copy the encrypted bootloader and other partitions. Therefor: keep the files safe.)

Why only working below 4.1?

Because after you upgraded to JellyBean you will not be able to install a custom bootloader. But this is needed to create the nvflash backup files. Asus made us a real PITA! After being on any JellyBean bootloader only Asus can install bootloaders. Because only they have the encryption key "to be let in". Or you can use nvflash, because the backed up files

are already encrypted for your device.

Again, my device TF300TG/TF300T is very similar in nvflash matters, but the prinicples are the same.

CWM and TWRP are custom recoveries. From the moment you "unlock your bootloader" with ASUS' unlock tool you are entitled to install any recovery compatible with your hardware.

The recovery has to be specific to the bootloader

(on TF300T(G)), so after

installing 4.1 or 4.2 you need a different TWRP or CWM

(read their homepage and/or device specific threads!).

Even if Asus removed the possibility to flash a custom recovery e.g. with the next JB update, you would be able to go back to the nvflash backup which enabled the old bootloader (e.g. 4.0) and let you install the desired recovery/custom ROMs/Stock ROMs.

Again, Asus cannot steal that nvflash option from you. You can always revert. (Again, I did not invent/research all of this by myself, I only spent days(!) reading the forum on these topics.)

Yes.

(But just be aware that you should make nandroid/Titanium Backup/app data backups as changing the ROM requires often to do a full wipe.)

If there are (substantial?) errors in this text, please PM or reply so that I can fix this. I really want to help, especially the new people. It is a pain if there are errors, especially when they are not corrected or only corrected 500+ posts later. ;)