How to unlock iPhone without passcode?

There are only 2 options for you. Both will require the phone to be erased. The first one does not require a computer and uses the Apple ID/Password if the Security Lockout screen is showing. It requires iOS 15.2 or greater.

If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support

If you are unable to use that option, then you will need a computer and have to follow this support article.

If you forgot your iPhone passcode - Apple Support

How to unlock iPhone without passcode?

This is not possible. This would be like asking how to unlock a safe without knowing the combination.

Don’t have passcode # for my daughter phone

Then, the phone must be erased and then set up again with a new passcode.

You might want to have talk with your daughter about the importance of writing down important information like passcodes and passwords and keeping them in a safe place.......even if your daughter is sure that she will never forget the information.

You can’t unlock an iPhone without its passcode