How to Identify fake Iphone

The only recommendation we can honestly offer is to only buy from trusted sources and ensure you can see the phone in person before you buy it. Read this link about buying used phones --> The All Too Common SAD Reality of Buying … - Apple Community

Assuming you can see the phone and know its serial number, you can enter it here to check whether there is any coverage or if the serial number is even recognized --> Check Your Service and Support Coverage - Apple Support

Fake iPhones are never really iPhones, they are Android phones with an interface made to look like iPhones.

Go to Settings>General>About. It will either show you it's an iPhone or an Android.

You can also look on your home screen for an app store icon, click on it. If it opens up the the Apple App Store, it is real. If it opens up to Android Play Store, you have a fake iPhone.

Turn it on. If you see the Apple, it’s an iPhone.