It's possible to get waivered in.... if your RE-4 was from a branch other than the Army. If you have an RE4 from any Army component, your odds of it happening are significantly less. It doesn't seem to make much sense, but bear in mind that we're talking about the Army, and not much about it ever does.
No.
no
No, you cannot.
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.
Depends on the specifics of your crime. You need to speak to a National Guard recruiter for a definitive answer on this.
Yes
Yes.
First, there is no Air Force National Guard. It is called the Air National Guard. The military does not train anyone to become a doctor. You would go to med. school yourself and upon completion of the course, join the Air Guard as a physician.
Depends on the type and for what condition.
It is usually not a bad idea.
yes