Cant open software for Updates

It isn't thrown away unless you do so. Facebook, Google, YouTube and others have decided to no longer support their apps on anything earlier than iOS 13 due to security and feature reasons. If you have an issue with that you need to contact them. The iPhone 6 does not have sufficient RAM to run iOS 13 or later and you cannot add RAM. You can recycle that iPhone with Apple.

Because versions higher than iOS 12 require hardware that does not exist in the iPhone 6. Sort of the same reason I can’t run Windows 11 on a 1984 IBM PC/XT.

Your 8+year old iPhone cannot be updated higher than 12.5.6

The iPhone 6 is too old. It does not have the horsepower needed to run newer operating systems.

You need a new phone.

iPhone 6 Plus can only be updated as far as iOS 12.5.6.

Chances are, you already have this version installed on your phone. To check......

Tap Settings.....Tap General......Tap Software Update

If iOS 12.5.6 is already installed, you have reached the end of the update road on the iPhone 6 Plus. To install, iOS 16, you will need at least an iPhone 8 or higher.

You can use Facebook, Google and Youtube with the Safari browser. You just can install the apps.