The safest way to do a Windows 10 repair without losing ANYTHING,is to have your computer on, unplug let restart, and repeat three times. This is used for many reasons including the inability to sign in. You won’t lose any personal files or apps. The only computer that does a true repair by unplugging one time and saves everything that I know of is the HP line of computers. There are a multitude of ways to reset and repair a computer, most go beyond the basic and start with the most advanced processes which in some cases can wipe everything including you’re secure drive. That ISO file is the easiest to screw up on if done from a USB. What they didn’t mention was, remove all plugged in devices and or peripherals, and you have to go into your boot menu and reselect which to load from. If you’re system jumps the gun and flickers on startup and passes the option to select to do a reinstall and or keep personal files to fast you will end up wiping EVERYTHING off you’re drives, including you secure drive with the backup Win Operating System that’s not a backup restore volume. Once you get everything completed do and entire backup of a high gig usb and store it in a safe place. To be honest, the Windows 10 Application is involving too much risk with glitched updates and between the three versions of cloud, Edge, Win 10 and if synced phone, it’s nothing but data being taken, and of course Google Play. Good Luck.