How can I know if my iPhone has been compromised?

naira225 wrote:

How can i know if someone close friend had already taken my phone and he knew my applle id password and done this before , he had linked all mu data. How i ll be able to find my own apple id and mu own apple device which iam using right now , what if someone has already used my data to link the other apple devices on my apple id and now its hard to differ my own original device , truely if hacked?

By hack, if you mean remotely controlling or monitoring your device, then...

Keep the iPhone updated to the latest iOS always and never Jailbreak. That's it.

iOS / iPadOS devices cannot be hacked or infected with Virus / Malware / Spyware if it is updated to the latest iOS/iPadOS unless you have intentionally downloaded spurious software or unauthorized apps directly from the internet and installed them on your device or/and have Jailbroken. 

It (Hacking) also depends on how careful are you in sharing sensitive and valuable information pertaining to your iPhone such as Passcode, Password, etc with your friends and family members.

Be careful when sharing the device's sensitive and valuable information with friends and family members.

Thumb Rules:

1. Enable  Guided Access before handing over an iPhone to kids
2. Don't share Apple IDs
3. Don't Jailbreak
4. Don't share sensitive information pertaining to your device and payment methods
5. Beware of Phishing

Probably you mean Apple ID compromised --> If you think your Apple ID has been compromised