For those of you who want to install custom ROMs on your LG G3, first you will want to learn how to make a backup ROM.
In this tutorial, we will show you how to backup and restore ROM on your rooted LG G3 using TWRP Recovery.
Backing up a ROM will backup your whole ROM (including kernel) along with your Apps, App Data and pretty much everything on your phone except personal files like photos, videos, etc…etc…
If you have lots of games on your phone, your backup may be larger than usual but a backup ROM usually is around 2GB.
I highly recommend using an OTG USB Flash Drive, this will keep all of your backup ROMs separate from your internal storage/micro-SD card.
First, you will obviously need a rooted LG G3 with TWRP Recovery installed. (At the time of writing this, TWRP recovery is only available for T-Mobile G3 but should be available for other variants soon.)
Step 1. Use Quick Boot app to reboot into your TWRP recovery.
Step 2. Choose “Backup” once in TWRP Recovery.
Step 3. Choose “Storage”.
Step 4. You can backup your ROM to your internal storage, micro SD card, or even OTG USB Flash drive.
Step 5. Next choose “Backup Name” if you want to set a custom backup name.
Step 6. Swipe to start backing up!
In my case, I had a couple games that were near 1 gig each so my total backup size became around 5.7GB.
Step 7. Once backup is complete, you are done backing up!
Step 8. If you ever end up in a bootloop or need to restore ROM, simply boot back into TWRP recovery. If you get stuck in bootloop, you can reboot into TWRP manually.
Step 9. Select “Storage” and choose the storage device you want to restore from.
Step 10. Choose the backup ROM you want to restore.
Then Swipe to begin restore process.
Step 11. Once done, reboot your system!
You should find your phone now restored completely back to how it was when you made the backup ROM.
This is a great way to make backup ROM of your stock ROM, so you can easily return it back to 100% stock if you wanted to.
Also, you can use this method to try different custom ROMs and save them as backup ROMs so you can always restore your favorite custom ROMs and switch between ROMs.