[Galaxy S 4 Q&A, Help & Troubleshooting] attmosphere:
Greetings

Dear s4 users I will share with you my experience with s4 i9500 and write the AIO (all in one) guide on the forum and keep it updated as much as I can and take into consideration every post u make.

INTRO: reason that make me writing this guide when my usb dead and I got panic cz my phone is 4 years old now and it dyeing by the time, fixed later by replacing usb board. I will put it later in troubleshoot. so I am now on stock firmware lollipop 5.0.1 last version. when I bored I will flash RR again.

So lets begin.....:

1-Custom rom:

LineageOS are awesome Omni and slim roms are great but the one that I prefer is RR it based on LineageOS source and combination between many roms to bring u stable, updated and the most customizable rom u ever found. I use it on my tab p5100 and s4 i9500 after I experienced so many roms

Current Stage: Beta

Current Ver : 5.8.3 android nougat 7.1.2

Current issues : echo effect in calls, 8 pit only no 11 pit support, OK Google doesn't work, u cant use ur sd as internel (cant move app to sd)

LINK: https://xdaforums.com/galaxy-s4/i9500-develop/rom-resurrection-remix-n-t3591063

2-Recovery:

my first exp was with philz touch recovery when twrp was untouchable, but it discontinued like s4.... :D

So Move on to twrp 3.1.1 last version from here https://dl.twrp.me/i9500/

3-Odin:

I use 3.10.6 cause most users recommended for lollipop from here http://odindownload.com/download/Odin3_v3.10.6.zip

4-Firmware:

u can download from this sites use last one for ur region or the most one near u for me I live in Lebanon and offcourse I don't have firmware for this small country so the most one near me Saudi Arabia (KSA) or United Arab emirates (XSG) or Egypt (EGY) or Turkey (TUR), for me I will discard turkey (different language) and Egypt (another continent), the rest is using the same baseband firmware XXUHOH6. (you can check urs by going to setting, about, baseband : I9500XX.......)

https://www.sammobile.com/firmwares/galaxy-s4/GT-I9500/

http://samsung-updates.com/device/?id=GT-I9500

http://updato.com/firmware-archive-select-model?q=i9500&exact=1

6-Bootloader and Modems:

I will not give u any links but I will tell u how to extract bootloader and modem from ur firmware

after you downloaded fw I9500................_HOME.tar.md5 u can extract it by winrar after u removed .md5 extension or by downloading Universal Extractor from here https://github.com/Bioruebe/UniExtract2/releases

u can flash ur modem (modem.bin) and bootloader (sboot.bin) by clicking CP in odin but if want to flash others like recovery or cache or boot.img (contains the kernel and ramdisk) that have .img extension, this script https://xdaforums.com/showthread.php?t=2446269 helped a lot all u have to do is just put ur .img or .bin files in the same directory and double click the .bat file and will have .tar.md5 to flash it in odin.

if you want more information about files trees and what every file for, check this thread https://xdaforums.com/showthread.php?t=443994

Some Useful code to use in dial pad:
*#06# IMEI
*#0808# USB SETTINGS
*#0011# SERVICE MODE
*#9090# SERVICE MODE

Troubleshooting:

when I downgrade my firmware to touch wiz kikat 4.4.2 custom rom I faced something strange that my default language changed to turkey and I had a Turkish app installed by default when I flashed back my region firmware, if you want to get back to original state try to flash modem.bin sboot.bin boot.img and then flash ur region firmware with enabled update bootloader in odin option. last tick in odin option menu.

WARNINGS:

TRY NOT TO DOWNGRADE YOUR FIRMWARE ITS DANGEROUS OPERTION THAT LEAD TO BRICK YOUR DEVICE

TO BE CONTINUED