Will I get a product key, can I get a product key?
By default, Windows 10 builds are pre-keyed, meaning, you do not have to enter a product key and should not be prompted to enter one even after Windows 10 has completed setup.
How to activate the latest Windows 10 build - Microsoft Community
Microsoft tells me that it will be possible to do so. And that a key part of this process is that it will save a product key tied to the previously upgraded PC or device in Windows Store. This is how Windows 10 will later know that the install is allowed: It's “one of the benefits of the new delivery system,†a Microsoft representative told me.
Source:
https://www.thurrott.com/windows/windows-10/3898/a-few-more-answers-about-windows-10-upgrades
Will ISO media be provided for the final release?
Yes, you will be able to download ISO media for Windows 10 RTM.
Please note, you might have to download the appropriate edition of Windows 10 for the version/edition of Windows you are upgrading. If you upgrade to the wrong edition, ie. Windows 7 Home Premium to Windows 10 Pro, you will have to purchase a license for Windows 10 Pro or go back to Windows 7 Home Premium and upgrade to Windows 10 Home.
What are the editions of Windows 10 available?
Suppose I need to reinstall Windows 10 after one or two years from now or I install a new hard disk?
Windows 10 is registered to the device, not your hard disk. Just install a new hard disk and reinstall Windows 10 and it will reactivate.