In melee, the infantry must be beaten first. Then the guns are vulnerable to melee attack. The rules say that units may change formation at the end of the movement phase. This would imply that artillery can unlimber and then fire in the attack phase. However, later on, it states that an artillery piece can never unlimber and then fire.
Artillery is a special case.
It can unlimber at the end of its move, but it can t fire that turn. There is an exception to this ruling under the Events Table. Per the rules on page 7, Formed units may pass though other formed units as long as they both make a standard Morale test. Both units would make Morale tests to check to see if they can interpenetrate. Thus, I would guess correct for your second answer.