Warning: Jailbreaking removes some security, but on a 10+ year old device, the risk is minimal.
A local proxy (e.g., a Raspberry Pi running youtube-legacy-proxy ) intercepts requests from the old YouTube app, translates API v2 calls to modern InnerTube API v3, and rewrites video URLs to MP4 formats compatible with the iPhone 4’s hardware decoder (H.264 Baseline 3.0, max 720p). Result: Native app works, but requires a home proxy. youtube for iphone 4 ios 7.1.2 download
YewTube is a lightweight, open-source proxy that strips down YouTube’s modern bloat and serves a basic HTML5 interface that iOS 7.1.2’s Safari understands perfectly. Warning: Jailbreaking removes some security, but on a