Title: Facebook on iOS 9.3.5: Is an IPA Worth It? (And How to Do It Safely)
Tip: If Facebook isn't in your "Purchased" list, you can "buy" it (it's free) on a newer iOS device or a computer using an older version of iTunes (12.6.5 or earlier), then it will show up in the Purchased section on your iOS 9 device. 2. Use the "Checkmate, Store!" Tweak (Requires Jailbreak)
Introduction
If you absolutely need the old app for nostalgia or testing, sideload with caution. Otherwise, Safari is your real friend here.