The answers themselves don't get changed, because that's not fair. That would leave a group of people who thought they had the right answer actually turn out to be wrong because a few people protested the answer. When you protest and if the MTA agrees, they throw out the question. They pretend it was never given, so everyone benefits. That's why everyone's score changes. The test would go from a 80 question test down to a 79 question test.
I don't know. I didn't attend the protest session. I would have, but I had other responsibilities to attend to. Though if anyone else went, I'd love to hear a report.