Question [Q] Problem with "stock" ROMS...

I have a Samsung Galaxy Note 3 (SM-N9005) initially with Android 4.3. I updated it to Android 4.4 with an stock ROM from Movistar South America ("CRM") and after that it became really slow, no sound and no camera. Because of that, later I flashed my phone with other ROMs from LatinAmerica and even with the british BTU ROM and the same: slow, no sound and no camera. I also lost IMEI, serial, baseband....

I'd like to go back to Android 4.3, but I know I can't. What to do? Which ROM to install?