I've bought an HTC One M8 at ebay a few days ago.. the device was sold as a Google Edition one, although, after I bought it, I realized that it was an unlocked HTC One M8 with a Google Edition rom (description in english wasn't so complete as the german one :P).. for me that wouldn't be a problem, although I would prefer to have the genuine firmware (I like the original HTC software)..therefore, I asked the user to change the firmware before sending the phone to me.
After receiving the phone, I've noticed that firmware version is "Android Revolution HD 8.1 by mike1986".. therefore,.. not the original rom from HTC.. besides this, there's also some "leftovers" of the google edition, as you can see in the image below (appears when I reboot the phone) .
The user told me that he has spent almost three hours to install that rom,.. and that he couldn't ger rid of the "Google" symbol whenever reboot the phone, as he had almost bricked the phone when he was trying.
What I would like to know is if there is the possibility to change the firmware to the original HTC firmware, exactly as if I was getting the phone from the store (with all the applications that comes with it) and that also allows me to benefit from HTC warranty?
If so, is there any step by step guide to safely do it?
I'm a novice in this area (never rooted or unrooted a phone).. and I just want to have the phone as if it was out of the box (do not need to have it unlocked to update roms or to delete any applications that comes with the phone, or something like that).
My HTC has a CID-HTC__102 (based on what I searched in the forum...it looks like an unlocked international version (German) device) and it has an IMEI SV 01 (I don't know if this info is needed, but I could not attach any more images, so I post this info here).
I will leave some info screen images as attachments so it becomes easier for you to help me.
Thank you in advance for your help.