-s (只寫入/system) Write /system. If you only want to update /system, this is the option for you. By default -s will attempt to preserve the kernel modules present on /system and overwrite the ones on the new /system image with those. This is appropriate if you've installed a custom kernel. -m (只寫入/firmware) Write /firmware (aka modem). -c (只寫入/cust.) Write /cust. Some files of these files appear related to VoLTE. I'm unsure whether they're critical or optional. One (seemingly harmless) error message generated when switching regions can be avoided by writing this area.