1 - duplicate contact option was there in the first place but merge all option does not work after many attempt.
any advice?
iPhone 12
You may have stored the same contacts in multiple email accounts.
Either remove the contacts from the rarely used email account or disable contacts from the rarely used mail account in the iOS Mail app.
Unlike some Android devices, contacts are neither stored locally on an iPhone nor in SIM. They are synced to an email account that you had Google, iCloud, AOL, Exchange, Outlook, Yahoo or any Other
iOS 16 missing duplicates contacts option
