I know it sounds shady, when I am coming back here again in few weeks, just been a bit busy lately, sorry about that.
However, somehow I got phone to flash it. The white graphical lines on sides dissapeared, however I got some new bug - I can't use phone in portrait mode, just in landscape - aka I need to swipe keyboard to have phone working. Also, that thing when phone completely stops working now occurs only when I am in that portrait mode, but I can restart phone this time.
When I finished this, it was midnight so I went to bad, so I tried to set up alarm, if it's gonna randomly shutdown like before and unfortunately, yes it did. I was waken up with this classical white line graphical bug black screen and had to reboot the phone. Oh well, managed to boot to system and it takes 5 minutes to fetch sim card (I have sim card mod from cornholio) and as I said, those white lines on side aka mysterious graphical bug is back.
Unfortunately for me, starts looking like real hardware issue now