Degree

Yes, it is a full time four year program.

No Vikas, advance Diploma is an undergraduate level course. Without a Bachelor's degree you cannot do Masters.

Hi,
The eligibility criteria is-
50 % minimum marks or equivalent grade point in psychology as core paper in BA.
MSU allows admission only if your degree is complete by the time your session here starts. That means, if they classes for MA start in June, then your Bachelor's should be completed by then. You shouldn't be still pursuing it.

Some major ground service providers like Indigo and Air India might not accept your distance education degree. But others who are basically involved as third party service providers like BWFS and Celebi will accept such a degree.

Yes, it's government approved.

It depends on college to college you must have to put the name here for that.

No, NLSIU offers only 5-year law course immediately after your 12th standard. There are several other universities where you can do three-year law.