I need to download the iOS16 app on my iPhone 7

You can't run iOS 16 on an iPhone 7. It does not have the hardware requirements for this OS. If you want iOS 16 you'll need to upgrade to a more recent model of phone

The iPhone 7 has reached the end-of-life support for Software Update to the latest iOS operating system (iOS 16 is no longer available).

You are invited to visit an Apple retail store to discuss your iPhone upgrade options.

Learn about the ⇢ iPhone Upgrade Program. 📲

Good luck! 👋🏼😉

iPhone 6 how to upgrade iOS 15.

Tnx

Re: “iPhone 6 how to upgrade iOS 15.”

You cannot. For the iPhone 6, iOS 12 is the end of the line.