Mega-telescope bid - South Africa vs Australia

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you dont, you steer the receiver instead giving the telescope a "limited" field of view.
in most scopes under construction that field of view is so large it barely matters though, many capable of focusing on several sky sections at once.

the chinese FAST will even include subsections for further fine tuning.

that said large interferometric arrays can become extremely powerfull as well but as far as i understand it they need to be synchronized and the further they are from eachother the harder that becomes.

**edit** it seems they are now using atomic clocks to sync the arrays but even then there is a chance of a desyncronized data stream due to the extreme fequency the signal operates at,
they could use quantum logic clocks but i dont know if any are in practical use today.

It's not only steering and field of vision but very large dishes can suffer from sagging due their mass just as big and heavy lenses can sag in large optical telescopes. I remember lecture where an engineer was saying that there is a maximum size at which single dish radio telescopes can be built before they would start becoming less and less sensitive at which point it would be better to use an array. That is why a telescope as sensitive as the SKA has to be done using arrays of smaller dishes rather than one big and is also one of the reasons why it is designed as an array, in addition to the cheaper cost of course.

Theoretically, if one were to colonize the moon, the back side of the moon would be an ideal place put a large radio telescope, not only because it would be shielded from the Earth's radio signals but also because one could put larger dishes there due to the lower gravity.

Yes, good decision.

There's an Australian information site here: Square Kilometre Array