[General Questions and Answers] jeremyb234:
Feel free to answer as much or as little of this post as possible. My desire is to learn. First, let me phrase my question in general terms:

1. Is it possible to download a stock android firmware rom, extract the rom, and change it, and repackage it in a way that is still accepted by the device as an original factory ROM? In other words, is it possible to take a factory rom (such as an update.zip or in my case 1.0.7.zip) and change it and reinstall it in the stock android system recovery (3e)?

Now that I have asked the general question, I will explain to you why I want to do this (if possible)

I have a tablet that recently stopped booting. I have never rooted it or used a custom rom before. However, the device still powers on and I can access the stock android recovery system. I can even use ADB (though I know very little about it's capabilities). I will explain my logic below. Please feel free to show me if I am wrong on the following points.

1. It is impossible to install a custom rom without FIRST installing a custom recovery.

2. It is impossible to install a custom recovery without FIRST rooting the device.

3. It is impossible to root a device that won't boot if you do not have USB Debugging enabled (via Android Developer Options).

The manufacturer of my device (RCA RCT6378W2) has not released the source code or original factory firmware for this device. I have attempted to install various roms that seem to be compatible via ADB SIDELOAD, but they have always been rejected immediately after the device says:

Finding update package...

Opening update package...

Verifying update package...

Installation aborted.​

However, I have managed to located 3 firmware updates from RCA. These updates are called 1.0.2.zip , 1.0.3.zip, and 1.0.7.zip. These updates are all accepted by the android system recovery. When I ADB Sideload these updates, the tablet says this:

Finding update package...

Opening update package...

Verifying update package...

Removing unneeded files...

Unpacking new files...

Install from ADB complete.​

Although these firmware updates are installed properly, my tablet still does not boot. Upon closer examination of these updates, they are not full android OS firmwares, but mere updates to the existing system. So, this got me to thinking... These updates are the only firmwares that can manage to pass update verification. Is it possible to alter these updates in a way that will still pass this verification process? If this is possible, then I might be able to reflash the rest of the android operating system by altering these updates to include the full OS. Does anyone know if this is possible? What would be the difficulty level of doing so? I have managed to locate nearly all of the files from another user who has the same device in working condition. For example, I have the following from a working device:

Backup.img

boot.img

cache.img

kernel.img

kpanic.img

misc.img

parameter.img

parameter.txt

recovery.img

system.img
​

Would it be possible to take the files from these images and add them to the firmware updates and repackage it in a way that passes system verification? And my last question is: Is there any other way I can get this device to a working version of android (stock, custom, I don't care!). Thanks!