Personal information
How do I know for sure if my device has been compromised
It's extremely unlikely your device has been compromised unless you let someone have it unlocked for an extended period of time with a computer. What makes you think it may be compromised?
There is no known method of remotely hacking an iPhone. As such no real steps exist to verify something that has no known method of happening.
What can be compromised is your Apple ID, but that does not mean your iPhone was hacked or accessed in any way.
See here if you believe your Apple ID is compromised: link-> If you think your Apple ID has been compromised - Apple Support