Windows 7 64 bit

I want to upgrade to windows 10 , and I know some features will be obsolete such as windows media player etc , but for instance I did not like windows 10 and wanted to change back to windows 7 , how would I do that ??

from the Microsoft Website:

If you want to go back to your previous operating system:

You'll need to reinstall your version of Windows from the recovery or installation media that came with your PC (typically DVD media). If you don't have recovery media:

For Windows 7 or Windows Vista: Before you update, you might be able to create recovery media from a recovery partition on your PC using software provided by your PC manufacturer. Check the support section of your PC manufacturer's website for more info.

Since I make backup images with macrium, that will work just as well, right?

This is one area I wonder much about :)

You could install one of the betas right now (at least in a virtual machine) and test that before commiting to a purchase. And you could take a full system image before installing anything and if things go bad you could restore it.