Yes.
Yes, they do. Puerto Rico also has a National Guard, as well.
You really need to speak with a National Guard recruiter about that. As the National Guard is a separate component from the Regular Army and Army Reserve, individual states do have some say in things such as age limits, and they may vary between states.
1 billion years :D
No.
No. Jackie Robinson served on active duty after having been drafted. The component where draftees are assigned to is known as the Army of the United States - the National Guard is an entirely separate component.
no
No, you cannot.
The Guard Recruiting Assistance Program offer part-time jobs to M-Day Air National Guard and M-Day Army National Guard members. The Army or Air National Guard can apply to be recruited into the program.
A loan default wouldn't disqualify you from joining the National Guard.
Not FOR joining the National Guard or Guard obligations, but that does not mean they can't fire you for other reasons.
You can enlist in the the Army, Army National Guard and Reserves until the age of 40, so you still have a few years to join.