Yes, a joint sponsor must be an LPR or USC. That's a threshold requirement for a joint sponsor.

In general, the N652 gives a summary of your case status up to your interview date. It excludes final checks that includes security checks, among...

Probably not. I'll suggest following up on your cases via the traditional means. Your mandamus action would likely be unsuccessful.

Even if case is dismissed but will be disclosed and may have adverse impact on future applications.

It is best to check the I864 instructions for a current methodology.

Your school DSO is a good place to start. Major ways to change status are through employment and family petitions.

Speak to a qualified immigration attorney to discuss viable options, if any.

It must be disclosed, and pertinent records submitted.

You may contact the court officials for an update on your PD filling.

Consult in private with a qualified attorney to review your specific case and discuss viable options.