[Onetouch Idol 3 Q&A, Help & Troubleshooting] printf():
This thread is meant as a guide to provide a higher level picture of what to do when your Idol 3 is bricked. This is not a step by step guide, some systems knowledge is expected.

Several hours ago all I had was a boot logo. Now I have Sailfish thanks to developers like vknecht and many other members who posted guides here and other forums.

Let's begin.

Requirements:

USB cable.

Sahara & Firehose Test software.

Appropriate TWRP image.

6045I Stock OS + Correct modem firmware. The OS and firmware comes in zips, unzip and replace and rezip as needed. My model was the 6045I so that was unnecessary.

Optional:

Your custom OS you wish to install. In my case it was LineageOS 14.1 and SailfishOS published by vknecht.

Stage 1:

The very first thing you need to do is to get the device to boot into /recovery partition which will hold the twrp.img. Doing this provides enough functionality to interact with your phone to unbrick it. To do this you need to:

Put the device into Download mode. It is done by connecting it via USB to PC (while it is off), pressing all 3 buttons - Power, Volume Up and Volume Down.

When screen prompts let go and hold Volume Up

The screen turns off. If the Qualcomm driver loaded successfully (in my case it automatically did), open Sahara & Firehose Test program.

All you need to do here is select your device from the dropdown > Click Detect (detects the driver) > NPRG > Get GPT > Info.

Now you need to scroll down and find the /recovery partition. Point the path to where your TWRP image is stored. The version of TWRP is important. For example, if you tried to install some custom boot chain that is not compatible with your OS you won't be able to get to /recovery. In my experience if you have the twrp-3.1.1-idol3.img and the twrp-3.0.0-1.img (from the hybrid boot loader thread) this was sufficient for my situation. Think logically which one you need to be able to load.

Checkmark the box.

Write the image (make sure to click No)

When you reboot your phone if you hold Volume Up you will have access to TWRP.

Stage 2:

Before you start modding anything just get it to load stock. Use the stock image from the thread link above, in my case it worked. However getting it to load will be a pain, depending on the situation. In my case I encountered /data partition errors. All errors regarding the /data partition are solved the same way - you delete it somehow. You are flashing an OS and your device is already a brick, data loss is acceptable. In my case I couldn't even mount /data (encryption issue) so I had to reformat it via the TWRP menu, make it first EXT2, then EXT4. Errors are irrelevant here, as long as EXT4 format succeeded you are good to go.

Stage 3:

Now use the standard procedure for flashing your target .zip via TWRP. In my case I deleted everything, /system (it was a brick anyway, just making sure it was clean), /data, /cache, Cache & Dalvik pretty much everything that made sense in my situation from the TWRP Wipe menu. I did this because at this stage you might encounter the infamous ERROR 7. There are different causes for it, but to know exactly why you got it open the updater-script file inside your extracted stock-rom.zip (META-INF\com\google\android was my location) via Notepad. This should tell you more about why you had the error.

Then flash the .zip. It worked for me.

Stage 4:

Once booted into the stock OS you are good to go. I don't know if you can get the OTA updates with that image, but I was upgrading to a more recent release of LineageOS so I didn't test long.

Earlier I mentioned you might need different TWRP images. This was the case for me here. After using the 3.0.0 recovery image I could boot into the OS but had difficulties booting into TWRP so I just flashed the 3.1.1 using the above methods and continued.

Once you are in TWRP you can use the standard procedures in other threads for flashing your custom OS. I was flashing LineageOS only as an intermediate step to go to Sailfish so I didn't flash GApps.

At this stage you might encounter ERROR 7 again, but for a different reason; If you deleted /data and you still had this issue it might be because of this. Basically it means you did not swap the radios like I told you to. You can either overwrite the script like suggested in this thread (it will cost you 4G) or you can go back and redo it.

Stage 5:

Boot into your custom OS. I think you get the method from here.

In short to go from brick to custom OS you need to get TWRP. If you can somehow boot into that, you can always fix the phone, and thanks to Sahara & FireHose Test program you should always be able to flash the /recovery partition as long as you find the right TWRP image.

Hope I helped someone, I was bashing my head for 3 days with this garbage Mobile Q Upgrade stuck at 20% issue some people have seen before.