Samsung Galaxy S3 with its official ROM cannot play Pokemon Go as it requires minimum Android 4.4 to run and Samsung stopped development at 4.3. However there is a way to play Pokemon Go on Galaxy S3 and it is not too difficult.
What you can do is flash something like S3 paranoid ROM that will bring android 6 marshmallow to S3 i9300. But if you want to have solid and stable experience, we suggest download and installing Ressurection remix along with Boeffla kernel.
You can download both and flash them in custom recovery one by one. For those who do not know, the Russurrection remix is based on cyanogen mod 13 and latest android 6.0.1 release. Installation instructions for ROM and kernel.
– Download the latest build
– Download Gapps https://www.androidfilehost.com/?w=files&flid=41043
– Take a nandroid backup
– Recommended – Full wipe and factory reset
– Flash ROM using latest TWRP 2.8.7.x Recovery
– Flash Gapps
– Flash kernel
And that is it – load up Pokemon go and play all day without any crash on your Samsung Galaxy S3. Just make sure not to install Facebook or any memory-eating app. You would want as much free memory as possible in order for it to not crash.