[Galaxy S III Q&A, Help & Troubleshooting] shivadow:
Just thought I'd chime in with some proper explanations.

Your phone has bogged down because the hardware is old now and most apps consume more CPU power than the phone can provide. Couple this with the ever expanding nature for RAM and the device will be under a lot of demand. Devices now are at least twice the hardware.

Now to the operating system itself. Android is not windows, nor linux, nor Unix. It is CLOSEST to Unix, derived from Linux and nowhere near windows even if you're blind and deaf and can't tell the difference. It really is a "bastard". The nature of android is to cache data for speed. Once this cache is full or resources run low, or android just can't kill an app for whatever reason it will bog the os down so bad the device will become unusable. I could demonstrate this VERY easily by filling up the internal memory with crap apps and dumb data and watch the device slow to a standstill (even the htc m9 I'm writing this on right now is susceptible). It's the nature of Android that causes the bogging down because it has run out of resources. It is THAT simple!.

Can we solve this bogging down by shutting down the offending apps with things like "greenify" or "hibernation"?.

The answer to that is "NO". Short and simple, you'll make the situation much worse if you attempt to hibernate apps. This is because the os will call for the app under its "normal allowances" which are defined by "permissions", you may have noticed these on some of the googleplay "read more" page when browsing an app. There are also permissions that you cannot see, one example would be "startup" which allows the app to start when the phone boots up. You CAN stop these startup apps at boot but if they continue to run you're best leaving that app alone. The reason being is that the OS will call the app, the app WILL respond. Then whatever app you're using to "control" other apps will detect the call and intervene, attempting to shut the process amd services down, the OS will detect this as a fail to load so it'll invoke (call) the process and service again, the "control" app steps in, rinse and repeat. Without knowing you've just waged a war in your phone between 2 apps and the OS. This will murder the resources and battery power.

So, after 2 years of normal operation your phone has become slow. You now know that the problem is that the phone is outdated because it is struggling to provide for the resource hungry apps that are out there (this is about as "in common" with windows as it gets).

Custom roms will be a waste of time. The reason is that custom roms are open source code, are very rarely optimised and not really compatible with the proprietary hardware they have to control. Although you can unlock extra potential it will be countered by the poorly written code. The custom rom will bog down in half the time of an official firmware.

I'm afraid I'll have to be the first to admit that your phone has now surpassed its life cycle. The only way to get better performance at this stage is to upgrade to a more powerful device. Not exactly the news you WANT to hear but it is the most honest advice you will find in this thread.

A LOT of people don't quite understand how android works as an operating system but they'll be quick to give you advice that is only partly true or not true at all.

The odin problem. Kies can be installed but the processes must NOT be running. Stop the kies processes in task manager.

As audit13 said, the output window in odin, we need to see that so we can determine whats wrong. We also need you to make sure you know what model s3 you have and that you have the correct firmware for your phone. Double check them in the settings menu.

Beamed in by telepathy.