Segregation will happen regardless of what measures are put in place, so the choice is between segregating by building or by neighborhood.
Well, that isn't true the questions are completely open here.
it's all part of the exact same development unless each section were given planning permission separately.
I don;t believe planning permission should be granted based on "we will build poor people housing somewhere else" it should be part of the main development if that is one of the main considerations for planning permission, affordable housing.
everyone living there should be treated as equals or not at all. (I'm not suggesting all apartments be built to the same standard but they should have access to the same communal spaces)
I'm not the one making the decisions and I don't know exactly how's it's decided, that doesn't mean I have to agree with it.
It's not about whether the three scenarios should occur - the question is given those three scenarios (all of which can and do occur in the UK).
Two of them involve the same site one of which is the same building and the other is separate blocks.
You've already answered that in scenario 1 you want them all to have access so you don't need to reiterate that - the addition question there is who pays for it and whether you see that as different to the other scenarios?