How do I prevent remote access to my iPhone?

No, but if they know your Apple ID and Password, they have access to your iCloud backups, which include the data on your iPhone.

Only provide your Apple ID and Password to those that you trust to never give it to anyone else.

Change your Apple ID Password as a precaution if you suspect foul play.

Bob Timmons wrote:

No, but if they know your Apple ID and Password, they have access to your iCloud backups, which include the data on your iPhone.

Only provide your Apple ID and Password to those that you trust to never give it to anyone else.

Change your Apple ID Password as a precaution if you suspect foul play.

Likewise, one should safeguard the local passcode or password of each iPhone, iPad, or Mac that's associated with one's Apple Account. Physical possession of the device + possession of the password or passcode could give an attacker access to synchronized data or even possibly the Apple Account.

Hello~ Click on below to change your password as *Bob Timmons* as suggested…

If you think your Apple Account has been compromised - Apple Support

~Katana-San~

Adding to the chorus of similar recommendations:

If you think your Apple Account has been compromised - Apple Support

… and …

Personal Safety User Guide - Apple Support

Findet5 wrote:

I've noticed that some features change themselves!

And what would those features be that change themselves.