Query on Common Area in Apartment with independent walls

I am staying in the Ground floor a G+3 storey apartment with independent walls. A beam runs through one of my external walls, below my flat's roof level. The beam is actually integrated with the external wall. External wall thickness is 8-inch and bean thickness is 10-inch, which means 2-inch of beam is visible outside the external wall of my apartment. I would like to know: 1) in an apartment with independent walls, is the outer side of external wall from floor level to roof level of an apartment considered as a common area or the flat owner's personal area ? 2) the beam is integrated in the external wall and is a part of it, so while one side of it protrudes 2-inch beyond the external wall, the other side is inline with the room's internal wall, below the roof level of the apartment. So is this beam considered a common area or a part of the the apartment external wall ? 3) if my neighbour wants to fix an external A/C unit on this beam integrated in my apartment's external wall, will it be an encroachment of my apartment ?