Questions regarding Two pipes Steam in 7 floors building in Argentina

Hi!, I live in the 7th floor of a 7 floor building.
The building has a two pipes steam heating installation.
I'm remodeling my flat and I want to apply some changes that involve taking out a radiator and maybe rotating the position of other radiators.
I read We Got Steam and tried to learn about how the steam works but there are a couple of questions that I'm not clear about.

Attached is the building heating pipes blueprint.

My questions:
I see that for each riser there is a vent on the roof, I'm not clear about this as in all examples I see the vents are in the basement. I also see vapor coming out often from those vents (not constantly, but in total it's almost half of the time the boiler is turned on.

In several rooms the steam pipes do a loop going over the radiator, I'm not sure if this has a reason or it's just because the installer wanted the radiator connections to face a specific way.

I have to remove a wall and want to remove a small radiator from that wall, my idea would be to close the pipes and disable that circuit, but I'm still not sure if that's allright or if in some way I would disable the radiators of that riser for all floors. Is there any situation in which taking out this radiator and blocking the pipes the whole line would not work for all the other floors?. In the blueprint it's this one:

Thanks for any help you can provide, I asked "experts" in my city but I'm not sure I trust what they are anwering me as I had answers that said that I couldn't close those pipes and other that said that it was ok, none of them explained exactly why.