Be sure to backup EFS and keep it on the external card / PC / in the cloud storage. Right now. Otherwise there may be a lot of things.go wrong.

Do not reset to factory settings via the firmware interface! Those who want to reset - readTHIS.

Before installing, carefully read the instructions "spoiler".

Archive firmware - in a technical post

The latest version of TWRP is strongly recommended for correct installation of the firmware and operation of OTA updates. | Download and discuss TWRP | TWRP FAQ

Newbies:
Transition from 4.3- the first steps. We get the root and custom recovery.
How to flash on custom Photo 4.3 without a computer
Very detailed instructions- install the firmware through custom recovery.
Manual update without data loss- update the already installed assembly.
Lineage OS downloads updates to/data/data/org.lineageos.updater/app_updates/

For those who want to return the stock - put your chosen stock(preferably service)via Odin(instruction)

There are no separate modems for these firmware. Newest laid outhere.

Google Apps (GApps) | FAQ
Open GApps Teamset: ARM | 7.1 (for 6.0 - 6.0) |Gapps set immediately. Together with firmware, kernel, etc.
An error occurred in the Setup Wizard application.- get rid of SetupWizard.
An error occurred in the Google Play Services application.- we set the rights to services.

Root
CM13 / 14:
Built into the firmware - to activate go to "Settings - For Developers - Superuser Mode"
Lineage OS:
Install this file using recovery:Download
Mass complaints that the file has ceased to be installed. The official root from the Lineage team, but with an alternative installation script here:
Samsung Galaxy S3 GT-I9300 - Unofficial firmware (OS 6.x.x- 7.x.x) (Post Hellsingoff # 61172026)

Or we put SuperSU (savagemessiahzine.com | XDA) through recovery |Warning for installing SuperSU

If you use SuperSU instead of the root pre-installed in the firmware, first install the kernel, then SuperSU.About the reasons we read here.
How to make a stock kernel before flashing custom

[N] - Compatibility mark with 7.0 according to users of this topic. Lack of tags does not mean lack of compatibility.
[N] - mark of lack of compatibility with 7.0. Exhibited at the time of editing, compatibility may appear later.


Instructions:
To take a screenshot, you need to hold the volume down + the power button.
Full cleaning system from GApps+ clearing fromC-Apps
If the camera crashes, we kill the mediaserver process with any application like this:Disable Service (alternatives)
Also against camera errors can help:Camerafix
[N] [M] Addon.d script to save SuperSU and Boeffla kernel when updating nightie
Script enable onscreen buttons and disable touch+ return to the original state.
Disable touch buttons
Volume up- in headphones and external speaker
[N] Edited sound file - deeper file edits
Cleanup script after firmware + iOS emoji + user dictionary + If after applying the script, an error is set up by Developers. + Version without cleaning
To remove the "public alert" - delete / freeze the application of the same name ordo so
Turn on ignoring unstable power.- if the phone is charging too slowly
Tweak patch- A set of tweaks for different parts of the firmware.

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Settings:
[N] Fix sound voice dynamics (who does not adjust the volume)
[N] [M] GPS Fix - we change GPS reception.
About the item weather (weather) in the settings- add weather source
Multi-window mode- where to turn on and how to manage
Manual setting SMS center(XDA, English) +Transferonsavagemessiahzine.com
Curtain and tile settings
Tips for reducing power consumption- energy consumption is discussed inprofile topic
Remove the bass external speaker- we cut the frequency spectrum of the external speaker, since it still does not know how to reproduce low frequencies (increases the volume and clarity of the external speaker sound)

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Memory:
[N] Transition to F2FS and re-internal memory - we change the file system and get 1.5 GB of space
About the new use of external MicroSD- screenshots, instructions, script return cards to normal
Solving the problem with recording to an external microSD- if recording to external card does not work
PC connection + addition + MTP auto power on
Transferring game cache to external card- mount the folder / Android / obb with an external MicroSD.

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Applications:
[N] Dialer with Russian characters for 7.x
[N] Fullscreen dialer for 7.x
SELinuxModeChanger- change selinux status
The solution to the problem with the recording of a river in Titanium Backup- we indicate the way to the river
If application freezing caused cyclic loading (bootloop)- script defrost all applications
For questions about changing the desktop interface - refer to the topic.Your hislauncher (Trebuchet- built in |Google Start- from GApps)
[N] Xposed - set "Framework for Android 6.0.x: ARMv7 (32-bit)"
Addon.d script for saving Xposed when updating nightie
DSP + for Marshmallow- advanced equalizer
Spirit2- radio
Call Recording- a couple of sample programs +alternative
Flashoncall- flash as a notification (for example, on an incoming call)
[N] В®DualBootPatcher - install multiple firmware instead of one. Instruction
CyanDelta Updater- update the "official" assembly SM with less traffic
В® CyanogenROM Downloader- OTA alternative to updating the "official" assemblies of the CM
Tasker- simple creation of scripts for all occasions (we add the missing functionality on our own)
Stock caller with photo on full screen- standard SM13 dialer, but with a photo of the caller in full screen.

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Appearance and interface:
Android O DP2 Emoji & Fonts- fonts and emoji from Android O
[N] Pixel ui - design in a new style.
iOS 10 Emoji- smiles from iOS 10
[N] Google pixel style
[N] [M] Hide SuperSu Icon - get rid of # in the status bar.
[N] HideNoDataIcon - remove the cross near the network icon when mobile data is turned off.
Topics for CM13 + If after installing the theme, you can not enter the theme application
Theme diy- create a theme for CM13 directly from your smartphone.