[T-Mobile LG G4] SignatureBoy:
Note : This guide is for H-81120-I & H-81120-O the latest update any firmware version below it will cause hard-brick so be careful before attempting anything, i wont be held responsible.

As a user with less knowledge about Commands and all, i was searching for answers by reading threads here and there and found my answers though some time tricky and sometimes easy.

Also in reading those threads i found many fellow members stumble upon resulting Soft bricks and in some cases a Hard brick or can say making their beloved G4 a paper weight.

So i thought i must put some really easy steps in order to clearly guide people like me who are too noob to understand the sophisticated developers steps.

Another reason for this Thread is also i saw many people asking about how to etc after updating to 20-O update for our H811 MM.

Few things to Prepare before Start

1- Properly Install Drivers for your H811 Variant of G4, cant find them Install LG Bridge.

2- Read the Whole thread before starting anything.

3- Confirm that all requirements are full filled and your variant is capable of everything mention in the OP.

4- Enable Developer Option then inside it enable OEM unlock and Usb debugging.

5- Always use Command prompt as Administrator.

6- Make a folder name G4 and paste all the file required for the unlocking in it for easy access and remembrance.

7- For Safer side after unlocking the bootloader boot into TWRP from fast boot and do not install TWRP.

8- Flash your SuperSU after that boot into android and see if all works.

9- Again Via Fastboot boot into TWRP make a backup of everything working fine. Boot into android.

0- Again same Via Fastboot boot into TWRP and now install your TWRP image via TWRP install function. So if by any means this is the culprit you can still revive your phone via your backup.

Attachments to Download

1- Adb Package can be found Here.

2- Download the latest TWRP.img 3.0+ from Here . This file needs to be on your computer and external sdcard.

3- Download the latest SuperSu zip (2.67+) from Here [Thanks to Chainfire] and stick on external sdcard as well.

Since downloading is complete now simply unzip the adb folder (containing fastboot by default) and paste both the TWRP image file and SUPERSU zip inside it.

Now Hold Shift and Open Command prompt here.

1- Input command to see if your device is visible in ADB.

adb devices

if you see your device and the status is off line then there will be a prompt on your G4 screen waiting for approval, accept it and input same command now all will be fine.

2- Now input below commands one by one. ( All credits to Autoprime )

adb reboot bootloader ( This will reboot your device to Fastboot mode )
fastboot oem unlock ( This will wipe all your data )
fastboot getvar unlocked ( This will check your bootloader status: Should be successful )
fastboot boot twrp-3.0.2-0-h811.img ( Phone boots TWRP ) Please put the full file name with .img extension or it wont work.

3- Now the Phone should be in TWRP install SuperSU from there which you have already pasted inside your external SD card.

4- Reboot to system and see if SuperSU is installed. In some cases First flash of SuperSU does not work if your case is same the again boot to Fastboot and from there boot into recovery, since your bootloader is unlocked no need to repeat the unlock OEM command.

5- Now for safer side follow the steps 7, 9, 0 mention in Preparation heading above.

Hopefully all will be in your favor.

Useful Links if you still fail

Kdz 20-O after download must be unzipped

H81120o_00_0613.kdz

LGUP Software:

( All credits to MicroMod777 )

Disclaimer: Nothing in this thread is my work, if i have missed any credit please do let me know i will add. I know several guides are available for same purpose so if any body finds it offending any rights can ask the moderators to remove this thread. The purpose only is to guide simple people like me to save their devices from getting bricked.