What Free Virus check is available for my iPhone 12

Your iPhone does not need apps to check for viruses. iOS is a secure operating system designed by Apple and is made to be secure and private. Your device protects itself from threats and automatically updates itself to stay secure. If you believe you are the victim of a cybersecurity attack, enable Lockdown Mode, here is how to do so: About Lockdown Mode - Apple Support.

Lockdown Mode is an optional, extreme protection that’s designed for the very few individuals who, because of who they are or what they do, might be personally targeted by some of the most sophisticated digital threats. Most people are never targeted by attacks of this nature.

Unless you've jailbroken your phone, you can't get viruses. AV apps are unnecessary.

Virus checkers or clean up apps are not needed on iPhone and considered useless. In most cases they will actually slow down your iPhone. Perhaps you can tell us why you think your iPhone has viruses and we can assist you.

Also the odds of your iPhone being hacked are nearly impossible. There are no known viruses that can affect your iPhone. The only way your iPhone could be hacked is if it was jail broken, which is still very difficult.