I got my Samsung S6 phone last end of June (2016) and it has been working fine. But after upgrading to higher version (Android N), the phone becomes unstable and slaggish, quite often, it's restart itself. I want to go back to earlier version when I bought the phone. But doing some research over internet, I couldn't find a place to download the firmware for Marshmallow 6.0.1 KDO.
Also, lots of posts mentions enable OEM unlocking, but I couldn't find that option at all in "Developer options" at all. Is this because Koodo doesn't give permission?