The Apple App Store is full of amazing apps that can integrate seamlessly with your iPhone's keyboard, allowing you to use them in Facebook Messenger, iMessage, WhatsApp, and more.

If you decide to download a modified APK from a reputable independent developer community (like XDA Developers):

Open your iPhone > General > Software Update to ensure your system emojis are current.

Using the Facebook Messenger iOS emoji APK is relatively straightforward. However, it's essential to note that installing an APK file on an iOS device is not as simple as it is on Android devices. To install the Facebook Messenger iOS emoji APK, users will need to jailbreak their device, which can void their warranty and potentially cause security risks. Alternatively, users can try sideloading the app using a third-party app store or a tool like Cydia Impactor.