Should I just contact ONE Prof at a University Grad Program?

I have read and I have been told that I should contact professors in the programs that I am interested in for graduate study.

Two questions about this.

1. Should I just stick to one professor in a program or contact a couple, whose research etc is in the same area that I am interested in?
A1: Contact the professor about the nature of the course, and about the graduate schools admissions requirements. Also, contact the Admissions Officer for that graduate program.

2. If I am interested in more than one program at a university but one of the professors whom I am interested in contacting is involved in both programs, should I just contact that one prof even though I am interested in the second prof’s research more?

A2: Ask the professor who works in both departments about an overview of those departments, and get their "comparison and contrast" (i.e.: Social Work vs. Psychology/Psychiatric Rehabilitation departments).

Anyone with experience contacting professors to get into a GRAD PROGRAM?
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C1: Have you reviewed their programs web-sites first?

Thanks in advance!!!