How to unlock iPhone without data loss using iCloud password?

Refer to this support article for various methods that you can use to resolve this. --> If you see an iPhone, iPad, or Apple Vision Pro unavailable message or Security Lockout screen - Apple Support

True, I often forget that, but I didn't get the impression that this was a new passcode though.

To be honest I cannot fathom the OPs who claim they forgot their passcode and their apple password. Mine are written down and burnt into my brain!

Forgetting…

Apple account password is understandable. I use mine almost every day but my wife can never remember hers since she only needs it a couple of times per year.

Passcode also understandable now that there's FaceID. Mind you, my iPhone only has Touch ID and every other day or so I get a passcode prompt when I want to use it. Not sure if a periodic prompt is part of iOS or just my fingers. Either way it keeps me on my toes about remembering my passcode.

LD150 wrote:

And, long story short, you cannot save the data on the phone that is not sync'd to a cloud or backed up.

You get a second chance to do a backup in this situation --> Temporarily use your old passcode when you forget your new passcode on iPhone or iPad - Apple Support

And, long story short, you cannot save the data on the phone that is not sync'd to a cloud or backed up.