Thanks ndi, you've been very comprehensive.

I like the possibility of overclocking my device, such as other things, but I prefer to learn everything about the device before doing this or any other.

Better than "Oh! Curiously this works!" I like better to know why some hack works, and what (and why) are the risks before customizing the system.

Nice to know the partition architecture: fast 256MiB flash memory for (read only?) root, and 32GiB for random write/access filesystems {2GiB for software and config + 30GiB in FAT for user documents}.

But now I discover that some versions of released firmware include independent firmwares for devices in the device (as GSM modem). Does it mean that GSM modem's firmware cannot be backup in the same way?