iPhone passcode forgotten, 8 hours not available, no recent backup

Your options are outlined at Temporarily use your old passcode when you forget your new passcode on iPhone or iPad - Apple Support

and If you forgot your iPhone passcode or your iPhone is disabled - Apple Support

Backing up is best done before the disaster, it is like fire insurance, impossible once the house burned down.

If you changed it more than 72 hours ago, or uour screen is playing up, your data that is not sync'd to a cloud of some sort will be lost.