1) one that is a software, not a hardware issue
2) many navigation programs running on iPhone offer turn by turn
3) no, Apple doesn't have an included turn by turn GPS program, yet
3rd party opportunity.
Google leverages its expertise in Maps to deliver this feature. They are in essence eating their own dog food.
Apple likely wouldn't do the same unless they saw the same sort of opportunity.
Google confirmed at a London press conference that it plans to bring free satnav to other smartphone platforms, including the iPhone, although it wouldn’t say when.