[Desire 816 Q&A, Help & Troubleshooting] Kakmnesu:
I fixed it myself and hope the advice can help someone:

A) Some of the mistakes i made during editing of the build.prop file

0. While bootlooping constantly hold volume down+power, it WILL boot to the bootloader after some time!

1. Don't use adb shell then adb pull/push, you don't need the shell here! Just use "adb pull /system/build.prop", notepad++ and "adb push build.prop /system/build.prop" to update the file, then set permissions again with "chmod 644 build.prop" and then "ls -l" to make sure the permissions of build.prop show -RW-R--R--

2. To use adb, get into fastboot->recovery and watch out that /system is mounted

3. Use the UniversalADBDriverSetup.msi to install drivers, then check check and check again that you change the drivers used to the ADB ones, not my htc, not android device. Different states of the phone sometimes activate different drivers (IE i plugged my bootloader phone in, changed drivers, got into recovery, had to change drivers again!)

4. Make a .bak file before you change anything inside android!

5. Avoid AROMA Filemanager, every time i tried to type something my keyboard got stuck and i had problems closing it. Without being able to remove the battery this is a huge risk.

B) Regarding OTA:

To disable the OTA updates i installed the app "MyAndroidTools" and disabled Service->System->Update/Upgrade(german: Aktualisierung)->UpdaterCheckIntranetService

Old Stuff:

Update: Got fastboot connecting, but adb not.

New main question: How to choose the rom i am going to flash?

Device	Carrier	Region	Type	Kernel	Android	Size	Description

Device is clear, but Region i get TW and TW Wifi. My android Version before was 4.4.2 and i had the ota upgrade to 1.60.xxxx. Is it safe to not know what carrier, region and type i have and just chose Region TW, Type CRC, Android version 4.4.2 1.54.xxx?

Desire 816 hTC Asia TW CRC 3.4.0 v4.4.2 155 MB 1.54.709.2

Can i use the latest android one instead?

Desire 816 APTG TW MR 3.4.0 v4.4.2 156 MB 1.63.500.1

TLTR: reboot loop after rooting and tampering with the build.prop file, can get into bootloader/recovery, usb drivers wont work, how to edit build.prop/reflash stock with zip/add new build.prop?

My Phone as i remember: TW international HTC 816 single sim android 4.4.2

PC win 7 x86 ultimate

Here is what i did before the bootloop:

Rooted the phone with this instruction: https://www.youtube.com/watch?v=vhUBLhdgSPU

Quote: 1. HTC Sync Manager 2. Install ADB Fastboot 3. Unlock Bootloader 4. CWM Auto-Install via ADB Fastboot / Bootloader 5. ALL IN ONE SuperSU .zip file for Internal Storage (Includes Busybox, Init.d Installer, & Write Protection Removal)

Then i wanted to hide the over the air update by modifying the build.prop with root explorer->Jota Text Editor

(renamed it to build.prop.bak first)

I couldn't save it in /system with Jota so i moved it to the location (editing or savind with wrong permissions caused the loop)

rebooting started the bootloop, every 4 minutes it will start again.

i could enter recovery mode holding down and power for some minutes.

then adb and htc sync didn't detect my phone.

i tried using a file explorer [CWM-APP][1.91] AROMA Filemanager + TERMINAL :: 130903 :: Open Source

from http://xdaforums.com/showthread.php?t=1646108 to rename the file, but the keyboard just hangs and produces garbage. Now my two build.prop files are named somewhat similar to jkdfh(ZG and $§BKGddddd, not build.prop and build.prop.bak

after barely closing the filemanager i am trying to get adb to work to change the filename for good

i boot in recovery and into hboot usb, connect the phone and try adb commands

i am now stuck, as none of the usb drivers i tried work.

i did a recovery->wipe data/factory reset and recovery ->wipe cache partition

i tried 15 sec adb drivers, i tried naked usb adb drivers, right now uninstalling every driver then reinstalling htc sync, reinstalling adb 15 sec 1.4.3 version of the drivers. Didn't find the ADB Driver entrys, so i searched and insalled universaladbdriversetup.msi, activated the "android adb interface" driver, have my phone in "fastboot usb mode", windows recognizes it, htc sync pops up but doesn't find a phone, adb still says device not found...

If i can't get the drivers to work, is there an option to not use usb to flash a stock rom from the sd (install zip)?

How do i decide what stock rom i need, how do i prepare it to be flashed as zip?

Please point me into the right direction.