Is it possible to make a complete image backup of phone and bootloader, without starting android OS or recovery mode - just swith off the phone, attach USB cable to PC, use software X to read all data as an image? (with preinstalled USB drivers for the phone)
And later restore that image with the same steps as above?
No. With the phone switched off you won't be able to back it up as your computer cannot detect it. And for an image backup, the system itself must not be running – which only leaves booting into recovery mode as an option, and then either doing a Nandroid backup or manually "clone" partitions (note that both would require a custom recovery).
The only other alternative requires special hardware and knowledge, see JTAG.
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