My iPhone 6 doesn’t allow me to install Facebook after reset everything why

If one or more of the following 6 options are true then you can't choose None as a payment method then the Billing information is needed . The "None" option will not appear...

1. If you have an unpaid balance or payment due
2. If you have a subscription that automatically renews
3. If you're using the iTunes Store or App Store for the first time
4. If you are not in the country or region you’re creating an Apple ID for
5. If you changed your country or region
6. If you're a part of Family Sharing

If you can't download, make purchases or update apps, including free apps, you need to update your payment method or add a new one. If you already verified that a payment method is available in your country or region and you're still having trouble, learn more.

The iPhone 6 cannot update further then ios 12.5.7 due to hardware limitations, as that iPhone Is too old to run modern day iOS versions. However, modern day apps need newer iOS versions. So if you want to use Facebook, you will need to buy a newer iPhone