How to update my iPhone to latest version?

You can update an iPhone 7 as far as the latest release of iOS 15. Currently that is iOS 15.8.2.

Update your iPhone or iPad - Apple Support

You cannot update an iPhone 7 to iOS 16 or later.

iOS 16 and iPadOS 16 are compatible with these devices - Apple Support

Notice how the iPhone 7 is not in that list.

No Apple device can be updated to iOS 14.1.4. The maximum version will depend on your device, but you have not provided that information.

How do I update my iPhone to 14.1.4vesion

How to update a 6s plus

Binmusa wrote:

How to update a 6s plus

Have you read the reply posted above? If so, what issues are you facing that are not covered by the included information?