Malo by to ist.
http://www.howtogeek.com/226100/the-windows-10-faq -everything-you-need-to-know/

If you rollback your machine in that first month you get your entire old Windows installation back. If you rollback after the 30 days you aren’t as much rolling back anymore as you are just releasing your Windows 10 license and freeing up your old key to be used for your older version of Windows. You’ll still need to totally reinstall Windows and use your old key to get your old installation back up and running.