How do I know if my MacBook Pro has an integrated or dual graphics?

I have a Macbook pro 15 Retina mid 2014 - A1398.

Initially the display wasn’t working, but if you shone a light through the Apple logo you could see the login screen, and it would work on a external display and I would detect both graphics cards. (screenshot attached)

I gave it to a service center (non Apple) they gave it back after some “tests” stating that there was a problem with the motherboard and they couldn’t do anything about it, it still worked on an external display but this time the Nvidia card was not being detected and shining a light through the apple logo didn’t show anything.

I informed the service center about this and they said they’d fix it, now they’ve completely killed it, when I connect it to an external display it shows a screen with horizontal stacked green and red stripes the apple logo and the loading bar and thats it (photo attached).

I’m told that the motherboard needs to be replaced.

So i’m now trying to figure out the correct motherboard for my system based on the Model Identifier - Macbook pro 11,2 or Macbook pro 11,3, and what the possible problem could be.

I’ve attached the graphics card information before it went kaput along with the Apple SN information.

Any help with this would be highly appreciated.