Not sure about this part, it varies, but I would be surprised if it is as low as 700 VAC on the primary side of the first transformer upstream of your house. I would think 2.4 kV would be a more likely minimum. But my familiarity with this part of the utility network is limited.
Basically yes. If we call the 3 wires on the transformer secondary A-N-B, where N is the neutral wire (the wire whose potential is always between the potential of wires A and B), then you can say that the voltage N-A and the voltage N-B are opposite to each other, or that they are 180 degrees apart. I think the "opposite each other" description is more apt, i.e. they differ by a multiple of -1.
Note also that if you look at the voltages A-N and N-B, those are identical (in theory, other than voltage drop, etc), so certainly in phase. And the voltages A-N and A-B differ by a factor of two, so also in phase with each other. There is only one phase present in this configuration, and any two voltages you can measure are in phase with each other.
Basically in a suitable sense 180 degrees apart is the same as 0 degrees apart, when just considering "phase".
Cheers, Wayne