How to download facebook in iphone 4s ios 7.1.2

Extracted from Whatsapp's supported devices:

WhatsApp for iPhone requires iOS 8 or later. On iOS 7.1.2, you can no longer create new accounts or reverify existing accounts. If WhatsApp is currently active on your iOS 7.1.2 device, you will be able to use it until February 1, 2020. iOS 6 and older are no longer supported.

If you're sure that your iPhone is a model "4s" (not a model 4), you can update it to iOS 9.3.5.

Regards

Giulio

Sorry I wrote about whatsapp, instead of Facebook. My fault.

It's the same problem, but you you need at least iOS version 9.0 or later.

Please forgive me.

Giulio