1) Its a framework. you can not access it at all. But that is not needed as well.
2) single click deploy but to run it on the xbox you need to have the $99 creators club membership
3) Sure, if you meet the needed quality. This is a console, so be aware that the process of approval and quality assurance will cost you $20'000 and more and that MS decides when the Q&A is met, not you
One important thing: If you intend to use XNA on desktop please keep in mind that it defines the minimum requirements as full Shader Model 2, so no casual game development with it as Intel at least till X3100 does not meet that (have not seen benchmarks of the 4500 yet so don't know if it finally got a shader processing unit that is capable of anything at all)
2) single click deploy but to run it on the xbox you need to have the $99 creators club membership
3) Sure, if you meet the needed quality. This is a console, so be aware that the process of approval and quality assurance will cost you $20'000 and more and that MS decides when the Q&A is met, not you
One important thing: If you intend to use XNA on desktop please keep in mind that it defines the minimum requirements as full Shader Model 2, so no casual game development with it as Intel at least till X3100 does not meet that (have not seen benchmarks of the 4500 yet so don't know if it finally got a shader processing unit that is capable of anything at all)