Radio system help

[MrWright]

Hi there I am new here and recently bought a 2012 Audi A4 B8.5 Avant Black Edition. The cars had a lot of work done which I’ve taken care of myself. 
 

One thing I’m unsure on is the radio system. I’m unsure wether it has or had nav? There is a slot for an SD card but is that just for media? There is also a button on the steering wheel stating “NAV” but it flashes up saying button not used?
 

I’ve also seen a few YouTube videos on the upgrade for apple car play etc with a junction box that sits between the radio module. Has anyone had any experience with these?

 

Any help would be appreciated and thanks in advance.