Use startup repair from Win 10 installation media, if it stops Windows from booting it should fix it. Once startup repair has run if it still won't boot go into your advanced options of the repair CD and select command prompt then run " sfc /scannow " this may take more than one time to repair everything. Also Windows 10 has a safe mode like every other Windows but now you have to enter it from the repair section of the installation media or hold down shift when you press restart in Windows