The fact is that If you Signe your build you will not be able to rollback to stock build with ADB update / ADB Sideload / SDRAM zip ... because your Bootloader check the signature.
The only way to do it is to flash the OTA or google Factory Build by Fastboot and for that you need your Bootloader to be unlocked.
Here's in red what i did wrong :
- Activate the "OEM Unlock" in Developer options.
- Unlocked the bootloader with Fastboot
- Flash my signed ROM
- At this time the "OEM Unlock" will turn Gray and we can no more use it to activate or desactivate.
- To test some security functions, i did re-lock my bootloader with fastboot. (Forgot that the OEM unlock is disabled).
Here's what i tryed in order to solve :
I did the steps discribed in [How-to] Unlock bootloader on Verizon Pixel/XL by burduli.
That did not solve my issue but it gives me an idea where to look for. Big Thanks to @burduli (Cedit to @Qu3ntin0 and @LeoTheRomRasta)
Here's the steps i did to solve :
No need to be on internet or so on
I did notice on the Device that there was a Guest User account but i had no way to remove it.
To do so i managed to :
1 - Wipe (factory reset) : Setting / System / Advanced / Reset options / Erase all data (Factory reset) => (Find the entry according to your Built / Android version)
2- Boot in Safe mode (Turn off the device / Hold the power on button till Google screen then release and hold pressed the volum down button until the device finish booting.
3- Go to setting / System / Advanced / Multiple users
4- tap on Guest, then on "Menu" the [...] on top right of the window
5- "Delete Guest User from this device" and confirm (It will seem like nothing done but don't stress it's ok)
6- Ones again Setting / System / Advanced / Reset options / Erase all data (Factory reset)
7- Your Device will reboot and at this time hold pressed the volum down button until the device finish booting (this time it will take longer to finish booting cause android is seting-up all stufs) . (that will boot the device in safe mode).
8- Enable Developer mode (tap 7 times on Build number under "About phone")
9 - Goto Developer options and you are done (The OEM unlock option is back and you can enable or disable it)
You can now reboot your device in normal mode .
In Booltloader mode you can use the "Fastboot flash unlock" or Fastboot OEM unlok command to unlock the bootloader