graphics card - Using laptop vga port, misunderstanding

I'm wondering if a VGA Monitor connected to the laptop, will act exactly as the inbuilt monitor?
More specifically:

1. I have the monitor connected to the laptop via VGA port.




2. I Start the laptop.




3. On Laptop's screen I see the Boot Screen, but on the VGA monitor I can't see anything until the OS system is loaded.

So the questions are:

1. What if I disconnect the inbuilt laptop's display, and connect the VGA monitor only, and boot? Would my laptop work 100% as if it was connected to its own display. Even without any OS ?




2. Is the VGA port controlled by the mother board or by the OS.

I know that on desktop motherboards which have embedded video card, there is no functional difference between using a PCI-express Video vs Embedded

Thank you!

Answer

What if I disconnect the inbuilt laptop's display, and connect the VGA monitor only, and boot? Would my laptop work 100% as if it was connected to its own display. Even without any OS ?

As I understand from these three forum threads, the display output ports are prioritized internally, perhaps in north-bridge chip (assuming you don't have integrated graphics like Intel HD series). And by 'prioritized internally' I mean you can not change it through BIOS options or from OS settings. Therefore, unless you disconnect your primary, in-built display, VGA output won't be able to take over the displaying task, meaning that the secondary display will not kick in until after the OS starts.

Is the VGA port controlled by the mother board or by the OS.

It's connected to either south bridge or north bridge, as seen in the wiki page I provided above.