Freelander 1 Another HK head unit question

Good evening !

Im the owner of Cherno the Freelander, HSE trim, and planning to swich the original Baker head unit by an Sony double din. I have the steering wheels controls and they are functionnal, the Sub is defectuous (making wrong noise) but thats all.

I discovered during the removal of my hu that only two connector from three are plugged : the large one (were from I suppose that all speakers are coming) and the antenna round one :

Then come my questions :
-Anyone can confirm the utility of the third small connector ? I understood that this one is driving the amp and the steering wheel controls, but mine are working and its the same for the amp (all speakers are working).

In order to put a new hu I need ISO cables, after searching there, I found these ones supposed to fit to my instalation :
https://incartec.co.uk/product/Landrover-Freelander-Steering-control-interface
-Can I order this one ? (then what to do with the third unplugged connector on my situation ?)

Thanks for your time !

Those ones aren't for your head unit if you have the sat nav unit, it's these cables you need :-

https://incartec.co.uk/Landrover/Freelander-facelift/Stereo-Upgrade-Double-Din/Sony-Double-din/146

Your supposed to use all of them. I have got them all but due to moving soon I am fitting my Kenwood double din after I move.

Thanks for your answer, so if I understood well I need these ones to have it working with a Sony double-din and a non-navi Harman Kardon setup :