Resetting laptop with Windows

I have a Lenovo laptop that I want to reset back to factory specs. The procedure will erase all apps and programs and reload the original operation system which was Windows 8.1. My question is I have already upgraded to Windows 10 for free. After doing the reset will I be able to get Windows 10 back or will the procedure reset the laptop to Windows 10?

Restoring back to factory specs is self explained. Your computer will be restored to the original operating system that was installed when you purchased the computer (In your case Windows 8.1). You can upgrade again to Windows 10 if you like afterwards.