[X3non]

if I flash the boot with sp flash tool I get the error as in the attached image. if I try with fastboot this wants the bootloader unlocked ... with all the consequences (loss imei etcetera)

is there any other problem aside from loss of imei after unlocking bootloader?
where you able to fix the invalid imei problem after unlocking bootloader OR is the imei still invalid?
where you also able to successfully root after unlocking bootloader using fastboot to flash patched_boot?
the rom you loaded into SPft in an attempt to flash patched_boot, was it the exact rom for your phone's build?