This is the easiest method if you have previously "purchased" YouTube on any Apple ID.
"Cannot connect to iTunes Store" error.
For users with devices stuck on iOS 9.3.5 (like the iPad 2 or mini), installing a working YouTube app requires bypassing current compatibility limits. While official support has ended, you can still get it running using "last compatible" downloads or manual .ipa installations. 1. Download the Last Compatible Version (No Jailbreak) youtube ipa file for ios 9.3.5