nardisk Hi,
Well, looks like you've gone too far. And the problem is getting even more complex now.
The basic rule that must be done before carrying out operations or modifications is BACKUP.
If you forget about this procedure, then the next steps may be more painful.
The new device has a security called ARB (Anti Roll Back) Protection, meaning if you flash a lower firmware version, the bootloader will refuse to boot, the way to fix this is to flash the same firmware or a higher version.
ISP is not connected, could be due to many factors, but formatting emmc before backup, this is the wrong step.
And don't continue with FFU upgrade operation.
Start by writing the stock firmware with the same version as the device's original firmware via Factory Image in the UFI eMMC ToolBox.
Exclude system.img, cache.img, vendor.img and userdata.img during writing process to check the booloader.
If the device can enter the logo, you can proceed to the next repair stage.
If it's still dead, then there's nothing you can do but replace the machine with new one.
B.R
