For users which really want to prevent Windows 10 from automatically installing updates, here are some methods to disable automatic updates. Depending on which method you use, you will still be able to manually check and install updates, or not be able to install updates at all...

Note that the methods leverage group policies, which is not supported on Windows 10 "Home/Essential" editions. A minimum of Windows 10 Pro or better is needed.

Caution
It is generally not recommended to disable automatic updates. Doing so (and not subsequently regularly installing the updates yourself) increases the risk of data loss and/or stealing due to potentional vulnerabilities in Windows 10.

The  ...

If you are not interested in Windows 10, but are plagued with the icon and prompts to upgrade to Windows 10, you can get rid of this. The Windows 10 Upgrade comes with Windows Update in KB3035583. You can uninstall this update in order to remove the Windows 10 Upgrade.

Note that after removal, you will have to hide the update from Windows Update to prevent it from being installed again.