Yes, as of 2008 - call any recruiter for confirmation.
yes
no
You are going to at least have a number assigned to you. If you are a resident alien, a local recruiter will advise you of what you will need.
If you have a green card, or can show proof that you have applied for a green card, you may enlist in the US Army as a foreign national.
No.
No, you cannot.
no
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.