iOS engineer here, it's not ridiculous for an app to require the most recent OS (which came out in September). However per the App Store, the American app's base OS is 10.3. Why do you think the issues are based on your OS version? Regardless, you should (always) update to the latest versions of the OS for security reasons.

Other things to try:
- Cellular (if you're on wifi, and vice-versa)
- Reset network settings (Settings > General > Reset)
- Hard reset (http://www.ubergizmo.com/how-to/how-...et-the-iphone/)