Every user wants to have the latest Windows updates and make sure that the computer has the newest release. However, some applications might have a hard time trying to keep up with Windows. As a consequence of that, sometimes you may discover that older releases are more compatible with some apps. For this reason, Microsoft still has ISO files for version 1607. You can also rollback a Windows update, but you are only able to do that in the first month. But what should you do if you want to return to an older version and you missed those 30 days?
Check the Microsoft Software Download page
Since this page only started hosting older versions after the 1607 release, this might not be very useful. However, it can help you if the Anniversary Update supports your computer.
If you search enough you will find some third party sites that still hold older Windows 10 versions. Some of them have all the releases. If you decide to get your release this way make sure you use a verifier to check its integrity first.
This is a simple method and all you have to do is create a Windows 10 recovery drive on a system that still has an older version. This is possible because the recovery partition does not get updated and it only takes into account the preinstalled Windows 10 version of your system.
Commercial licensing programs
If you are willing to try an expensive option you can take a look at Microsoft Software Developer Network or Volume Licensing. Here you can find any version, but you will have to pay in order to get it. While it is pricey, it is also the safest method on the list.