I have done some searching in google and the forums but it always doesn't match my question. So if an admin sees this and finds a the really same one, sorry!
To start, I have a SHV-E370K, which is a equivalent of the s4 mini, only it's only sold in Korea. It's carrier branded... which is kinda good, because you get all these goodies!
What I did to my phone is far surprising. I installed a custom rom straightaway, not knowing I tripped the KNOX counter. I have no idea if installing a custom recovery and rom unlocked my bootloader.. but I'll let that be.
By the way, I used cm 11 nightly.
And suddenly I'm tired of cm, so I downloaded the stock rom and flashed it. And suddenly, no wifi, bluetooth, no data, nothing. Not even a startup sound. I read somewhere that flashing a older rom had negative consequences, so I found a fresh recent rom and everything was okay.
But then, I suddenly found that NFC was disabled. I clicked to re-enable it. It hung there for maybe 30 seconds, then unchecked itself. I am so damn sure I just wrecked a $800 gadget.
Someone please help me... This bus card app thing needs NFC...