Never flash p2-bootloader-mbr or anything to address 0 (when using SWD). Doing so will permanently render the device unbootable.
And under most circumstances you don't need to manually flash the system parts or bootloader. Just have your firmware target Device OS 5.4.0 in the Web IDE or Particle Workbench and flash it to your device. The other parts will upgrade automatically over-the-air.