[X 2014 Q&A, Help & Troubleshooting] AceT2213:
I bought a Moto X (2014) with a broken/damaged screen for super cheap. When I bought it, it vibrated and made sounds so I knew it was functional. The next day, the alarm woke me up so I turned it off. The day after it happened again, so I just let it ring under a pillow until the phone died. Yesterday, the screen replacement finally arrived and I performed the switch myself.

When I tested the screen before closing it back up, the phone wouldn't boot, but the screen itself appeared to be functional so I closed it back up. The infamous green light issue was occurring, no doubt due to the fact that I let the battery drain completely then left it in a drawer for about a month, in addition to God knows what the previous owner had done to it.

After several hours of hooking it up to various chargers and cables and computers and performing a seemingly infinite number and duration of button combinations, it finally booted up, and started to charge normally.

Only then I realized it was still protected by the pattern code from the previous owner. Due to fear of FRP, I kept trying to crack the pattern code to no avail. Eventually I said frick it and went into bootloader mode to try and unlock the bootloader, but it turns out that adb is not enabled, and neither is the "allow bootloader unlock". So I said frick it and hit factory to reset the phone, but the phone simply rebooted. Odd. Alright, so I hooked it up to a computer in bootloader mode and performed fastboot erase userdata. Upon reboot, FRP had kicked in.

Hours of searching yielded various methods of bypassing this, none of which worked. However due to the blessing/curse (more on that later) that it's on Marshmallow, I was able to use a Google Assistant loophole to access pretty much the entire device (minus Google apps, including the play store). This included the settings app. To my dismay, I'm unable to activate dev options and the reset button is greyed out, no doubt due to a group policy preventing these functions until the owner's Google account is entered.

I came across a method that showed a lot of promise. Through the use of an app called Quick Shortcut Manager, it allows you to log into any Google account and once you reboot afterwards, FRP is no longer an issue. However in my case, since I seem to be exceptionally lucky, during the sign in process, the phone reboots unexpectedly. How very odd. Retried several times under various conditions, including Force Stopping all Google apps (which returns the navbar buttons, without function, and also the notification tray but not quick settings).

Alright. I installed Telegram via apk and logged in. As soon as I logged in, the phone reboots unexpectedly again, which leads me to believe that this random reboot occurs whenever ANY account is added to the device (because Telegram accounts are saved under Settings > Accounts).

Knowing I'm stuck with a locked bootloader and no way of unlocking it without accessing dev options which I'm unable to do, I decided to try flashing an earlier build. I downloaded 4.4.4 and 5.0.1 factory images and proceeded to try flashing 4.4.4, to no avail, since apparently downgrading is also impossible with a locked bootloader. Most commands returned a "remote failure" response. I continued anyway and upon reboot I discover that nothing has changed. I've tried this with both system images.

I tried RSD Lite as well but it won't even detect the phone in fastboot/bootloader mode (on Windows 10 Insider Preview). Tried with admin privileges. The "fastboot flash" option in the Config menu was greyed out for some reason.

I've hit a roadblock. I'm so ready to just toss this phone out the window but I decided to come here and ask for help first. Please, XDA. Do not fail me.

P.S. I've lost contact with the owner because I bought the phone on a local equivalent of Craigslist so neither the ad nor my communication with him still exists. And even if by some miracle I managed to find one, it would do me no favors if he would remove the account via Google Device Manager because I've already reset it. The only thing he can do for me is log into the phone using his email and password and then reset it, which would require going somewhere with WiFi that is also public all the while making sure he doesn't try to steal the phone back now that it's fixed.

Edit 2: Ever since I added the Telegram account, the phone is no longer usable, since it reboots unexpectedly as soon as it connects to WiFi and discovers that an account has been added to the device. I'm going to reset it again so I can continue using it with these limitations.