Resetting iPhone 1
Grandpa passed away. Don’t know iCloud password to reset to factory setting of a very old iPhone
Contact Apple. They need to see a copy of the death certificate and a copy of the will or a document that shows you inherited it.
How to request access to a deceased family member's Apple accounts - Apple Support.
Apple ID - Official Apple Support.
Contact Apple for help with Apple ID account security - Apple Support. (Link doesn’t always load)
Get Support Work through the screens to get a chat option.
Apple Support schedule phone call
https://twitter.com/AppleSupport People have posted it may take an hour or more to get a response.