Does building firmware recreates bootloader

I am trying to understand building APM firmware. I am using older APM 2.8.
Does building firmware recreates bootloader and part of the build output? I have tried Visual studio with Arduino Micro plugin but there are errors due to missing library.
Can i use special APM arduino software to directly upload code to APM 2.8 as it compiles the code successfully? What are all the implications i need to consider.

I think that on APM2.8 it use arduino bootloader. But we discard support for those cards years ago.
So no idea how it works …

Okay. When i use visual studio with the micro, i am getting “object is not referenced to an object instance” and “An error occurred while deep search for libraries”. Any idea? All libraries are in place.

In this article it explains that for non pixhauk, chibios open pilot hardware, we need to upload ardupilot bootloader for first use. Is my understanding correct?

this is for STM based board like Pixhawk. APM2.8 is AtmelMega so you cannot use this.
As said before, we don’t support those board anymore, so you need to find some old instruction about how to build Ardupilot 3.2 on APM2.8

I am planning to buy other autopilot and would like to understand the process. So if it is STM based autopilot came with other autopilot software, is it must to flash the bootloader with ardupilot bootloader firmware.
Thanks in advance