And how to try beta version 1 iOS 18 on iPhone 11,12?

iOS 18 beta software is currently only available to developers. Public betas will be released in the future. See: Apple Beta

Yeah, it's only available to developers...

1. Download XCODE (Developers App)
2. Sign in (Apple ID)
3. You have access to developer beta!

it worked for me

If you want to wait until the release of the Public Beta... July

Kiril90 wrote:

How to install iOS 18 beta 1?

Unless you have a spare phone and need iOS 18 for testing software, I recommend against it. This early in the beta cycle, you could end up with a non-working phone.

Either wait for the public beta or download developer beta.