Note pro update to Android 9 guide.

Hello everybody. While digging through the Onyx Boox FB page, I found this link to an update to Android 9 of the Note pro and Nova pro, in flash mode and at our own risk. This appears to be a successful update and not a beta version with inevitable bugs. It's strange that Onyx Boox isn't communicating more about this important update. I have just successfully updated my Note pro to firmware 3.1 and I would be tempted to update my Note pro e-reader (currently running Android 6) to Android 9. Has anyone tried this yet. adventure? With success ? With what difficulties? A big thank you in advance for your responses. I can not put the link. Onyx Boox specifies in fact: "(...) Please do not distribute or download the flashing guide and package on any platform. BOOX official is not responsible for any product malfunction caused by unauthorized flashing." but I think you will find it quite easily via a search on Facebook or elsewhere!
I downloaded the software for the upgrade from Android 6 to Android 9 as well as a tutorial, all specific to my Onyx Boox Note pro e-reader. It seems more complex to me than with the Likebook Mars (Boyue) e-reader.
I am carefully rereading the update guide. I ask you the following questions:
1 / Should the uncompressed "Updater.rar" folder be placed in the root folder of the pc or does it matter little?
2 / In step 11 it is mentioned: "Ensure your BOOX is power-off. Press and hold Back button, then connect it to the Windows 10 PC with an original USB cable to enter Flashing mode." Is the "back button" the small hole located just next to the mini usb port? When we say: “Press and hold Back button”, we actually have to push a reset “needle” into this hole and keep it pressed ”? This is the maneuver I made with our Likebook Mars (Boyue) .