iPhone X and earlier iPhones will not have this feature of iOS 15

However, most of these new features will only appear on iPhone models from iPhone XS and above.

Here are the features that won't be available on iPhone X or earlier models:

1. Portrait mode during FaceTime calls, blurs the background and puts the focus on you
2. Partial Audio in FaceTime, making the voice appear to appear from the direction the user is sitting when making a call
3. Voice Isolation mode in FaceTime, uses machine learning to block out environmental sounds such as fans, neighbor dogs barking.
4. Wide Spectrum mode in FaceTime, which amplifies background noise during calls. In contrast to Voice Isolation, Wide Spectrum helps everyone on a FaceTime call hear everything that's going on around you.
5. Interactive 3D map of the Earth in the Maps app
6. Detailed pedestrian directions with step-by-step directions displayed in an augmented reality in the Maps app
7. Detailed maps of major cities like San Francisco, Los Angeles, New York and London in the Maps app
8. Live Text to copy and paste, look up or translate text in images
9. Process voice commands you ask Siri right on the device
10. Siri can perform your requests such as calling, texting, sharing, running apps, controlling music and opening settings offline, no internet required.
11. Ability to swipe up or down while recording a QuickTake video to zoom far or close
12. Possibility to unlock house, hotel and car keys into the Wallet app
13. All keyboard dictation on the device is done offline
14. Continuous keyboard dictation instead of 60 seconds limit each time
15. New live wallpapers in the weather app (Weather) to more accurately represent the sun's position, clouds and precipitation.

Looking at the list above, we can see that Apple requires the iPhone to use the A12 Bionic chip or higher to support the new features of iOS 15. Apple does not give any explanation on this issue. However, most likely the above features need Apple's 2nd generation Neural Engine or higher to run smoothly.

Details about the new features of iOS 15 you can read here.