as Justin said, check your Hard drive for errors. may need replacing. plenty of guides on the net.
do you have a windows installion disk/usb? if so, set it as your boot drive in bios (tapping either F2 or DEL or F11 or F12 repeatedly when ASUS logo appears) and try startup repair.
And your FN keys/Backlit keyboard lights problem is from either not having the ATK driver installed, or your Intel Management Engine Interface driver is not right (i had this problem caused from Intels latest driver is crap and Win10 auto installs it)
if you have the ATK installed, try go to device manager/ system devices/ Right click Intel Management Engine Interface/ properties/ uninstall driver, then reboot. if no joy and Win 10, you may manually install the right driver, but first you need to set windows NOT to manage the drivers.
(not recommended if you dont know how to install drivers for your system manually)