How do I know that my iPhone is hacked?

You know that it is not hacked unless you have left the iPhone with someone else for 30-60 minutes and provided your Apple ID and Password to the person.

Any messages or emails that you receive that state that your phone has been hacked are scams that are trying to sell you useless software or worse........trying to get you to reveal personal info. NEVER click or tap on a link in a scam message.