Did you manage to download and create a Windows 10 installation Disk or USB device and if so were you able use either of those media to bootup to the Windows 10 installation screen?
Also, pressing F12 during the computer startup, as you have indicated, usually displays an options screen to select a a device to boot from, which is NOT the same as the Safe Mode options screen. If rapid pressing of the F8 key is not displaying a Safe Mode menu, then it may indicate that Windows 10 is still attempting to startup your system, hence my previous question re: do you now have a working Windows 10 Installation Disk or USB device?
is it a DELL computer that you are having this problem with?
Another thing to check before booting is that you have no USB device plugged in and no disks in the CD/DVD drive to ensure your system is not attempting to boot from one of those devices.