The is limited to iOS 7.1.2 as its final official software version. Because the current version of Meta's Messenger app requires much newer software, downloading it directly from the App Store on an iPhone 4 is often restricted. How to Download Messenger on iOS 7.1.2
If a popup appears stating the current version is incompatible, select to install the "last compatible version" for your device. Alternatives if the App Won't Install Messenger For Iphone 4 Ios 7.1.2 Download