Hi, recently my iPhone 8 has been freezing with the screen still on, but both the home and power buttons not functioning. this would usually go away after i plugged it in for a few minutes, but now it seems to have completely died with the screen completely black and the home button still pushable, but plugging it in or doing any of the reset tricks doesn't seem to help. on a separate note i have it updated up to ios 15, but for some reason when i tried to download any apps that required ios 9 or later it wouldn't let me. any help or suggestions would be very appreciated.