Looking for general advice about CIDs, S-OFF, debranding and running RUUs?

Hi, all...

My M8 is bootloader unlocked, rooted (with Chainfire 2.46) and TWRP 2.8.7.0 custom recovery installed, and just recently I spent to acquire S-OFF. Currently, there are no problems or issues with it.

A few days ago, I received the libStageFright (and Lollipop 5.0.2 update) OTA for CID: H3G__001.

(It's available here if anybody wants it.)

I didn't allow it to install for reasons which will become obvious in the next paragraph...

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From what I've been reading here on XDA over the past few weeks, if rooted, simply unrooting and fastboot flashing the stock recovery isn't sufficient to allow the OTA.

Indeed, the various accounts I've read here on XDA seem to indicate that allowing the OTA causes bootloop/softbrick, remedied only by one of two options...

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i) Restoring an unmodified/unrooted NANDROID backup.

- or -

ii) Running an RUU.

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The first isn't an option for me, since I can't find an unrooted NANDROID backup for H3G__001. Leaving only the second option, of running an RUU.

(And which is why I bought Sunshine/S-OFF two weeks ago.)

The precise command line arguments don't concern me at the moment. I'm just looking for general clarification on several points of principle before I proceed.

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I have several general questions...

-- As I understand it, with S-OFF, I can now pretty much flash what I want on my M8.

-- In order for me to run an RUU, I understand I may need to re-write my CID from H3G__001 to [what exactly???]

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My M8 is on the 3Mobile network in the United Kingdom.

** Which CID should I choose? What is recommended?

** Or is it obvious I just use Super-CID?
That's Globally Universal... right? Or am I wrong?
Super-CID is better? yes or no?

** What is the difference between a WWE CID and Super-CID? Or am I misunderstanding something here?

** Would my 3Mobile network SIM be recognized on the 3Mobile network once I've changed my CID?

** Would I need to also change my MID to run an RUU, and if so, to what?

** Finally, what RUU should I run?

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I'm just looking for general guidance here; some pointers really - I can take care of the fine details myself.

I'm in no immediate hurry to do any of this... patience is my watchword... but I'd like to understand exactly what I'm about to do before I do it.

I'm not concerned about wiping the device, nor am I concerned about loosing root. These are mere trifles. Root can re-acquired and all my data is safely backed up on my laptop... including a TWRP Nandroid of my current setup, should I need it in the event of any foul ups.

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Apologies if my questions have been dealt with elsewhere and please feel absolutely free to tell me to come back after I've read every post on this forum if you think I'm clueless :) (...and you probably wouldn't be too far wrong :( ).

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My ultimate goal here is simple... I want to 'convert' my M8 into a device I can simply and easily reflash by running an RUU, similar in some regards to reflashing Google Factory stock images on my Nexus 7 or Nexus 9 tablets... and where I don't have to worry about rooting it and then not being able to take the next OTA... and where I can just simply reflash back to stock in the event of some Xposed Module gone wrong... or perhaps maybe after experimenting with some Custom ROMs.

Right now, I don't feel I have complete control of my M8, and acquiring S-OFF was my first step in changing that. I just need some help/advice/pointers in the right direction.

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I've spent weeks reading everything I can... But the time is drawing near when I need to stop reading and start doing... I mean, I've paid for S-OFF... I might as well start availing myself of the benefits it confers :):):).

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Thanks in advance, guys.

Cheers, all...

Rgrds,
Ged.