[One (M8) Q&A, Help & Troubleshooting] syntropic:
I had an app installed called Android Tweaker Pro (or something like that). It was a legitimate Play Store App [although it was later removed along with many other apps as Google wanted to eliminate apps that had "Android" in the app name.] However, the real problem is that it was a root app and it was originally designed for Kit Kat.

I had not really touched it since I upgraded to Lollipop, and when I was running Kit Kat, it worked great... it has numerous tweaks (mainly to build.prop), however, in the past, I typically used an option in the app called "auto tweaker" which changed a certain set of variables. It was a safe route, as it clearly warned you up front not to enable all of the tweaks.

Well, I opened it tonight, and changed a few settings... I believe I changed/increased the video fps, and I think I optimized the LED flash, and I also enabled the "Power Supply", which the app explained reduced battery use if it was turned on.. But I don't think any of those things were really that big of a deal.

However, there are two more things I did that may be the cause of my problems:

ONE: I foolishly set the Dalvik Heap SIze to 0K. (I think it had a max of 512K). I don't know why I did that exactly... I think I assumed Dalvik wasn't being used in Lollipop, so I thought it would free up memory.... it was a total clueless move I realize, and of course feel like an idiot.

SECOND: I zipaligned all of my apps. I didn't think to look up if zipaligning apps was necessary anymore... which was also foolish I realize.,

Anyway, after it finished zipaligning my apps, I rebooted. The splash screen and then the T-Mobile animation ran but then froze at the HTC ONE screen. I powered it off a few times and tried to restart again—but there was no change... My phone was just frozen at that boot screen after the animation.

I booted into recovery, and the only thing I did was rename the Android Tweaker "base.apk" to "base.apk.bak", but I didn't really think that would help. I also tried to find the build.prop file to see if by chance the tweaker app made an automatic backup so I could restore it....but had no luck finding it the build.prop file at all... It doesn't seem to be where it used to be prior to Android 5.

So what I am hoping to do is find out where Lollipop keeps its build.prop file (or whatever it's equivalent is now)...and see if there was a backup made and restore it. IF not, then I am looking for suggestions.

On the other hand, if this is because I zipaligned all of my apps.... then I have no idea what to do.... Please offer suggestions. I will be eternally grateful!!!

Note: I think I can do a factory restore, but I cannot lose what is on my extended storage, so unless I can backup extended storage using adb (which I would think doubtful given I cannot boot into the phone), I really, really do not want to do a factory reset.

My sincere appreciation in advance for any help suggested!!!!!!!!

EDIT: If it helps at all, I am currently S-Off (with an unlocked bootloader), and I have an old nandroid backup. It is pre-Lollipop upgrade. SO...absolute worst case scenario (aside from losing my phone altogether), is to restore Kit Kat, and then do the OTA again...restore all my apps, etc. But I cannot imagine there is just some file I could delete using TWRP recovery that would be regenerated upon boot.

If I had to restore the KIT Kat nandroid and do the OTA, it would just take several hours...And it is 5:00am where I am and I need to use my phone by 8am.... SO, I hope someone has some alternative. I would settle for a way to back up my extended storage, and then somehow push a rooted nandroid of lollipop on the the storage and restore that with TWRP....

Any other ideas are appreciate of course!!!!!!!!!!!!!!!