While the iPhone 4 is limited to iOS 7.1.2 and no longer officially supports the latest YouTube app, you can still access YouTube using several workarounds. Method 1: Download Last Compatible Version (No Jailbreak)
Apple does provide a fallback: when attempting to download a modern app on an old iOS version, the App Store server offers the . For YouTube on iOS 7.1.2, this is YouTube v10.11.11546 (released March 2017). youtube for iphone 4 ios 7.1.2 download
: Tools like TubeRepair or manually editing the Info.plist file (changing the version string to something like 14.02 ) can sometimes trick the app into working again. While the iPhone 4 is limited to iOS 7
However, due to compatibility issues and the discontinuation of support for older iOS versions, the latest YouTube app versions might not be compatible with iOS 7.1.2. : Tools like TubeRepair or manually editing the Info