Hi! I understand your situation. It can be frustrating when you purchase a device only to find out that certain apps are no longer compatible due to its older version. However, it is important to note that sharing Apple IDs, even for the purpose of downloading apps, is generally not recommended as it can compromise the security and privacy of both parties involved.
Instead of sharing Apple IDs, I would suggest exploring alternative solutions to your issue. For example, you can try accessing Facebook and YøùTùbé through their mobile websites using the Safari browser on the iPhone 6. While this may not provide the same experience as using the dedicated apps, it can still allow you to access the platforms and their content.
Another option is to see if there are third-party apps available on the App Store that might provide similar functionality to Facebook and YøùTùbé and are compatible with the iPhone 6's older version.
If these solutions do not meet your needs, you may consider upgrading to a newer device that supports the latest versions of the apps you require. This would ensure a better user experience and access to all the latest features.
I hope you find a suitable solution to your concern. If you have any more questions or need further assistance, feel free to ask. Good luck!