Flash OS and Rooting - ronaldyho/hacking_Mobile GitHub Wiki

Install OS image / Firmware

Quick links to some of the tools necessary to reflash Android devices

DOWNLOAD the latest firmware

Samsung

Frija tool (WIN)
https://forum.xda-developers.com/s10-plus/how-to/tool-frija-samsung-firmware-downloader-t3910594

https://updato.com

MediaTek
https://spflashtools.com/

SIDELOAD via tool

Samsung

Odin tool
https://odindownload.com/download/

Understanding the Android builds

Breaking down the build numbers:

https://source.android.com/setup/start/build-numbers

PVBB.YYMMDD.bbb[.Cn]

P represents the first letter of the codename of the platform release, for example, O is Oreo.
V represents a supported vertical. By convention, P represents the primary platform branch.
BB is an alphanumeric code that allows Google to identify the exact code branch the build was made from.
YYMMDD identifies the date when the release is branched from or synced with the development branch. It's not always the exact date at which a build was made as it's common for minor variations added to an existing build to re-use the same date code as the existing build.
bbb identifies individual versions related to the same date code, sequentially starting with 001.
Cn is an optional, alphanumeric that identifies a hotfix on top of an existing PVBB.YYMMDD.bbb build, starting from A1.

Components

AP / PDA - Application Processor (System Partition)
CP - Core Processor / Modem
BL - Bootloader
PIT - Partition information table
CSC - Consumer Software Customization; Flashing HOME CSC file keeps data intact; using the other CSC will wipe data.
USERDATA - is where all the Carrier customizations are. Flashing USERDATA will also wipe data.

Components and its numbers

Note that sometimes you might not be able to downgrade from a higher Android version to a lower one. One of the reasons may be that your current bootloader version is higher than your target's version.

PDA / AP

G930F XX U2E REM
G973F XX U9D TJA

As shown in the image the first 5 letters (eg: G930F) is your phone's model number. 
The next two letters (eg: XX) denotes the country/ region code. 
Now the next 3 letters denotes the bootloader version (eg: U2E) of your phone, in this example the bootloader version is "2". 
The last 3 letters denotes the release date (REM), in the example "R" means "2018", "E" means May and "M" means the date.

CSC

A700FD OLB 1BOJ1

As shown in the above image "A700FD" denotes Galaxy A7 2015 dual SIM model 
and the country code "OLB" denotes Malaysia, Philippines, Thailand or Vietnam

REFERENCES

Detailed explanation of PDA and CSC codes, https://www.samsungsfour.com/tutorials/all-samsung-galaxy-firmware-pda-and-csc-codes-list-with-detailed-explanation.html
About the different firmwares, https://forum.xda-developers.com/t/g960u-and-g960u1-firmware-links-here.3763388/

Download IPSW for iOS

Downloading the IPSW to be loaded via XCode (or iTunes)
https://ipsw.dev/ios/14.x/

Rooting Android Devices

Unlock Bootloader
Load TWRP (Custom Recovery)
Load Custom Rom
Install Systemless Root (i.e. Magisk via TWRP) - If you use Magisk, you will need to install Magisk Manager too