Root Telus Rogers Koodo LG G4 H812 by downgrading from Marshmallow to LollyPop

There is  no root available for LG G4 H812 Marshmallow (MM) devices now, but root is available for LollyPop (LP). The strategy here is to downgrade to LP from MM and root the device. You need to disable the OTA updates, since the root will be lost if you upgrade.

1. Download stock KDZ from https://forum.xda-developers.com/g4/general/canadian-guide-complete-source-lg-g4-t3212449
   1. I downloaded "H81210n_00_1204STOCKkdz". All carriers are cross compatible (Bell, Rogers, Telus, Wind)
   2. If you have downloaded 10n kdz, you should download 10n rooted image. I downloaded "H81210nROOTEDrogers.rar"
2. Downgrade from Marshmallow to LP https://forum.xda-developers.com/g4/help/lgup-install-kdz-mm-lp-t3249803
   1. TO GO BACK TO LP FROM MM - Open LGUP on your computer, select "Upgrade", click on FILE PATH and point it towards your LP KDZ. Close LGUP and re-open LGUP. Make sure you select REFURBISH this will do a full wipe, tick BIN file. Press Start. Make cup of tea and be patient 
      
      If you are worried about losing your data after a full wipe, why not use the LG Bridge software to backup and restore.... it works fine!
      YOU WILL LOSE ROOT!
      There is no need to enter download mode! LGUP will do it for you.
3. Install ROOT https://www.reddit.com/r/lgg4/comments/3ir4zn/guide_how_to_root_all_versions/
1. Use dd if=/data/media/0/rootedsystem.img bs=8192 seek=65536 count=548352 of=/dev/block/mmcblk0 for H812 (all Canadian carriers LG G4)
4. Install Xposed using https://forum.xda-developers.com/g4/themes-apps/guide-installing-xposed-locked-t3181593
1. Follow instructions below worked for me
2. Download FlashFire version 0.24, and xposed-v87-sdk22-arm64.zip
3. Set your date of phone back to June 2015 .
4. v0.24 has only one option (Auto-mount), which I left unchecked.
5. 20 minutes of blank screen, then some flashfire text and a reboot, it optimized apps, and then finished normally.
6. Install the xposed installer apk (XposedInstaller_3.0_alpha4.apk) and it reports v87 is active 

Installing CyanogenMod 7 (mil version) ROM on Koodo LG optimus One Android phone (P500h)

Root the phone before doing this.

Download cyanogen_thunderg-ota-eng.mil-6.5.4.zip into your microSD card. CyanogenMod 7 ROM is based on Gingerbread. Install ROM Manager on your phone. Open ROM Manager and select Install ROM from SD card. Now browse to the downloaded cyanogen zip and tap it.

In the menu, check backup existing ROM (if you want to back up the current OS, highly recommended). Check the options to wipe data/cache and dalvik cache. Now Tap OK. The phone will restart and backup the files and then proceed to CM7 installation.

The phone will automatically restart after the installation (takes about 5-10 min). You will see a brand new OS on your phone. Go to settings and add your google account to synchronize contacts, mails etc.

If you want any other google applications which are not already installed with CyanogenMod 7, follow these instructions.

The same procedure can be used for installing any other android ROMs.

ALL CREDITS TO ORIGINAL DEVELOPERS.

Install google apps on your new Android OS.

If you want any other google applications which are not already installed with your current Android ROM (like CyanogenMod 7), download apps-addon.zip. If you don't have it already, install ROM Manager on your phone. Open ROM Manager and select Install ROM from SD card. Now browse to the downloaded zip file and tap it.

In the menu, check backup existing ROM (if you want to back up the current OS, not required in this case for installing google apps). Uncheck the options to wipe data/cache and dalvik cache. Now Tap OK. The phone will restart and backup the files and then proceed to gapps installation.

ALL CREDITS TO ORIGINAL DEVELOPERS.

Rooting Koodo LG optimus One Android phone (P500h)

This procedure will work for LG optimus One Android phone from Koodo (P500h). This may work for other LG Optimus One phones as well, but I have not tested it.

Do not use z4root to root this phone (many people suggested to use this, but didn't work for me at all). The process takes forever without any result.

Download GingerBreak-v1.20.apk (google it, I am sure you will find it). In the application settings, allow installation of non-market applications and enable "USB debugging" in Application settings>Development. Once you install the apk, you will be able to do a "Permanent root" without any fuss.

Please leave a comment, if you have success with any other methods.

If you want to go ahead and install a new ROM (for eg cyanogenMOD 7) instructions are here.