Can I choose which ios to install on my iphone 15 pro? ios 26 or ios 18

What version of iOS is the phone running now?

If it is running iOS 26, you can't downgrade. If it has automatic updates turned ON, it probably is running iOS 26 – or will soon update itself to iOS 26, after which you won't be able to downgrade.

If it has automatic upgrades turned off, and is on iOS 18, you might be offered both

• An update to iOS 26
• An update to the latest release of iOS 18

You might be shown the iOS 26 offer first, then have to go out of the Software Update screen and back in (or, e.g., scroll to the bottom of the screen) to see the iOS 18 offer.

If it is on something earlier than iOS 18, my guess is that Apple is no longer offering iOS 18 – the only major update offered will be iOS 26.

No, you cannot choose. iOS 18 is no longer available for download or installation. If your iPhone 15 Pro is already running iOS 18 it can be updated to the latest version of iOS 18. But if it is already running iOS 26 it canont be downgraded. As for AI you are not forced to use it. Simply don’t enable it. Apple Intelligence is not enabled by default. You have to turn it on.

Why do you not “trust” AI? It’s not going to give you false information anymore than a Google search does. Most people seem to be using it as a smarter search engine anyway. You don't have to use it to write an article if you don’t want to. Any technology can be used for both good and bad. I think you’ve been reading too many conspiracy theories about AI.

But the bottom line is you have control. Don’t want it? Don’t turn it on.

I believe you can still update to iOS 18.7 over the air on an eligible iPhone. That window will surely disappear in the not too distant future. As to Apple Intelligence, your phone will either already have it or it will be installed when you update it. But you don't have to use Apple Intelligence if you don't want to use it. I'm not sure why you wouldn't want iOS 26. I've been running iOS 26 on my devices since it was released and it's in my opinion great.

Hopefully your son has prepared the iPhone 15 Pro for a new owner, as described here:

What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

If so, when you turn on the phone, it should start up to the "Hello" screen. If it doesn't, ask him to complete the steps under "If you no longer have your iPhone or iPad."

Once the phone starts up to the "Hello" screen, you can use Quick Start. It looks like there's a variant that works with iCloud – and another that works by holding your old phone close to your new one.

Set up iPhone - Official Apple Support

Use Quick Start to transfer data to a new iPhone or iPad - Apple Support

I concur.