[T-Mobile LG G3] Frankenscript:
Hi everyone,

I'm the new owner of an unlocked T-Mo D851, and will be using it on AT&T. I bought the T-Mo version instead of the ATT version due to the unlocked bootloader and better Dev support. Love those Devs!

I figured I'd post a thread with the things I learn along the way, to help others that might benefit, particularly since I'm joining the G3 community long after the novelty has worn off. Folks like me that join have a lot of past experience to review here, and so much is out of date it can be intimidating, particularly when our new device acts a lot different from our old one. I hope this thread helps someone, but at minimum it will serve as documentation for me to refer back to, should I need that. I'll include links where appropriate.

I'm an intermediate level flasher, having worked with maybe 6-8 other phones/tablets. So, I know enough to be dangerous, but not enough to have an ego to bruise. My most recent phone was a T-Mo Galaxy S4. But I dropped it, and cracked the screen, just a few weeks after getting it all settled in with a nice 5.1.1 GPE ROM. Sigh.

I got the phone a few days ago but have just gotten around to working on it.

On day 1 I charged it up, skipped setup (touch corners, upper left, upper right, lower right above the softkeys, lower left above the softkeys... took 10 tries or so!), and connected the wifi (no sim card inserted yet). It immediately found update 20E (it shipped with kitkat). I let that update, but was surprised it didn't find the current 20G update. I want to make sure I start with the latest firmware/modems etc. installed.

In this thread, helpful user [MENTION=5993314]mitbit2k3[/MENTION] pointed me to the online LG site that lets you download the LG Mobile Support Tool. It also gives instructions for installing the PROPER PC connection driver for the phone which works, versus the default Win7 driver that doesn't work for the purposes of the update. With proper driver installed, and with USB connection in the right mode (follow instructions to set the phone USB settings), I got up to 20G stock.

I exercised the phone a bit (still without SIM card) and made sure everything worked... cameras, GPS, wifi, etc.

Then I figured it would be time to install TWRP and take it from there. Much to my surprise, you need to root this thing FIRST. Even with an unlocked bootloader, you can't just fire up ODIN and flash TWRP.

I did my research on the forum and through Google... with all the versions of software since release there were numerous descriptions of how to root the thing, some of which were outdated. For me, on 20G software (5.01 Android), this worked fine:

https://www.reddit.com/r/LGG3/comments/3n0nk1/new_super_easy_oneclick_way_to_root_g3/

it references back to XDA of course:

http://xdaforums.com/lg-g3/general/guide-root-method-lg-devices-t3129197

From this I learned to review the top level LG G3 subforums, not just the T-Mobile XDA subforums!!

OK, that rooted me just fine and installed SuperSU. I was able to use the "first way" which is super simple.

With that done, I was able to install TWRP. I went straight to the source for it:

https://twrp.me/devices/lgg3tmo.html

I used the "dd" method which involves running ADB on the PC. I use a version that is a "Minimal ADB and Fastboot" that works fine... I used it to mess around with my Shield tablet previously, so I was familiar with it. Basically you run the minimal ADB through a desktop icon, and it loads a command line interface. You type ADB Shell after plugging in the phone to the USB cable (it has to be on, developer options enabled, debugging enabled). Then you type the commands listed on the TWRP site. Pretty soon TWRP is installed.

Next I had to figure out how to get into download mode. Yeah, yeah... power plus volume down... been there done that, but on the LG you have to boot with power/down, then when the LG icon comes up you release for a second, then press the two keys again, then at the next screen tell it you want to wipe the phone, and confirm this again on the next screen. THEN it finally boots into TWRP. Kinda scary. And getting the keys right takes some practice.

Once in TWRP, I backed everything up (including EFS partition) to an external SD card, just in case I messed something up. I had previously erased the SD card from within the phone's SEttings/Storage mode, to make sure it would be able to be accessed. No problem.

So now I've got a rooted phone, with TWRP installed, and the next step is to figure out what I want to do ROM wise. I wish there were a 5.1.1 GPE stock + LG Camera ROM. But I haven't found one. I like plain ROMs. The default stock ROM, even if it were debloated, its a bit annoying to me (and just 5.0.1) so I'll probably move to BlissPop or Slim something, but I will research around.

It's time to stick my SIM in and see how the phone does on AT&T. I'd like to get a baseline before I go ROM-hopping.

I will say that on stock ROM, with no SIM but WIFI on, the standby power drain on this thing is incredible. It went overnight (7 hours) and was still reading 100%. A whole 24 hours in, it was only a few percent lower. Of course, I hadn't attached any Google accounts, so the phone was truly idle, but it's very impressive nonetheless.

Stay tuned. I'll be updating this as I go along.