How do I check if my iPhone is hacked using iCloud email?

Why do you think your device has been "hacked"? Because of all the security features Apple has around its equipment this is incredibly costly and difficult to achieve —> https://security.apple.com/blog/memory-integrity-enforcement/ Much more likely is your account may be compromised, giving another user access to your account on your hardware. Even account access is surrounded by a number of security features but is more easily compromised by hackers convincing people to reveal security information, or users not bothering with implementing Apple’s security features.

Read this article if you think your Apple Account has been compromised. --> If you think your Apple Account has been compromised - Apple Support

Use the information in this article to check your Apple ID device list to find where you're signed in --> Review devices signed in to your Apple Account - Apple Support

Related materials:

Personal Safety User Guide

Personal Safety User Guide - Apple Support > open the Table of Contents and review the articles

An article with general information about security and your Apple ID --> Security and your Apple Account - Apple Support

Contact Apple for help with Apple ID account security. This page provides country-specific Apple Support contact information ➞ Contact Apple Support - Apple Support