How to install iOS 16.6 on my iPhone 7 Plus?

It is not possible. The latest iOS the iPhone 7 received was iOS 15.

If you are trying to install an application that requires that version, you might need to try using the website of that app instead, or consider upgrading to a newer iPhone like the iPhone SE. It’s similar to the 7 but has newer technology that can update to the current version of iOS.

Apple Vision Pro requires iOS 17.2 or later version, unfortunately not compatible with an iPhone 7 Plus, because of hardware (CPU/RAM) limit.

Regards

Giulio

If you’re trying to say you wan to install iOS 16 on your iPhone 7 Plus, you can’t do that.

iOS 16 requires and iPhone 8 or newer.