How to unlock the PandoraBox Bootloader in PandoraBox Firmware

(1) I have flashed the pandorabox bootloader(pb-boot) and pandorabox firmware into my Xiaomi R3G router.

(2) Now I want to revert back the stock firmware, then I can flash the openwrt/pandavan firmware.

(3) But the bootloader partition seems to be locked to prevent from changing to other bootloader.

(4) Can someone help me and show the correct steps to revert back the stock firmware.

(5) And share the Xiaomi R3G router factory mtd partition backup files as shown below.

root@XiaoQiang:~# cat /proc/mtd
dev:    size   erasesize  name
mtd0: 07f80000 00020000 "ALL"
mtd1: 00080000 00020000 "Bootloader"
mtd2: 00040000 00020000 "Config"
mtd3: 00040000 00020000 "Bdata"
mtd4: 00040000 00020000 "Factory"
mtd5: 00040000 00020000 "crash"
mtd6: 00040000 00020000 "crash_syslog"
mtd7: 00040000 00020000 "reserved0"
mtd8: 00400000 00020000 "kernel0"
mtd9: 00400000 00020000 "kernel1"
mtd10: 02000000 00020000 "rootfs0"
mtd11: 02000000 00020000 "rootfs1"
mtd12: 03580000 00020000 "overlay"
mtd13: 012a6000 0001f000 "ubi_rootfs"
mtd14: 030ec000 0001f000 "data"

Thanks in advance.