If the facts are as you report them, your "peer" has committed academic misconduct.
- Your "fellow peers" didn't get caught.
- No, the instructor is not responsible for preparing a different exam; the professor should be able to rely on the integrity of university students. In any case, a fair separate exam would necessarily cover the same material.
- Probably the the professor should have told the student with the advance exam to keep it confidential, but I'll bet if you look in your student handbook, you'll find a statement about illicit knowledge of exam contents.
- No, it comes down to someone revealing the contents of an exam to students who have not yet taken it.
- See Anonymous Mathematician's answer concerning Facebook: "Why not?"
- See Anonymous Mathematician's answer concerning Facebook: "Only if the Facebook account was hacked."
Your "peer" knew what he was doing was wrong and he did it anyway. Now he must accept the consequences of that action.
Edit: It has been pointed out that this answer is generally in the context of higher education in the United States. Given that a professor accused a student of academic misconduct for breaching the integrity of an exam, I expect it applies in the context of OP's question even though the institution is not in the U.S.