Root and installing Recovery ROM on LG D855 (G3) for custom ROM

If you have a updated LG G3 e.g. LP or MM, you may find getting root access is quite hard. I have found a way to root it and install custom ROM.

Disclaimer: I will NOT be responsible for any damage on your D855 G3 on trying method in this article. Try on your own risk.

Before you go, you have following ready:

1. LG Flash Tool
2. LG D855 firmware (v10b 4.4.2) 
3. Strump tool  <- br="" d855="" firmware="" for="" initial="" release="" still="" work="">
4. LG G3 855 modem (21C) 
5. TWRP recovery rom 
6. a PC with adb tool installed (e.g. Ubnutu 15.10 or Windows 10 with Android SDK installed) 

Step:

1. Boot D855 to download mode (power off -> press vol up and connect USB to PC)
2. Run LG Flash Tool to flash 4.4.2 firmware
3. Install Strump and run Strump tool (reboot D855 afterwards)
4. enable USB debug mode
5. install SuperSU from Google Play 
6. copy TWRP image to SD Card of D855 e.g. adb push /storage/ external_SD/
7. enter D855 shell i.e. "adb shell"
8. change to super user i.e. "su"
9. dd if= of=/dev/block/platform/msm_sdcc.1/by-name/recovery
10. boot to recovery mode(in TWRP now)
11. Flash 21C modem by TWRP
12. reboot to TWRP
13. you can flash LP or MM custom ROM now 

 credit : 
hyelton  xda developer (flash stock rom steps)
jcase xda developer  (strump tool)
step_han (provide flashable modems) 

LG (flash tool)
TeamWin (recovery rom developer)


 This is the way what I tried to flash custom ROM on D855 with LP stock ROM installed.