3 rbi triple
When the batter is standing on the plate.
a home run
When you touch the plate. That is a called a run.
It is the base that the batter stands at to hit a pitch. This base must be touched to score a run.
If the batter/runner is contacted by a fair ball when they are out of the box they are out and the ball is dead thus no runners can advance. Given this the answer to you question is no they can not score.
2 unassisted. Any batter or runner called out on account of a rule is scored as the action of the nearest player.
60% (failing)
Home-plate since that is where the most important person in the game is, the batter. It is also where the score is made that determines the outcome of the game.
If the walk off home run scores another runner that was already on base and that was the run to win it then there is no need for him to cross the plate and he is not called out. For example, in a tie game with the bases loaded if the batter hits a home run the only run that needs to cross the plate is the runner on third. Once that runner crosses the game is over and any more scoring becomes redundant so the game ends on the score sheet. If it is a solo shot or if the hitters run is detrimental to his or her team winning the game than the batter must cross the plate for the run to count.
If the runner is attempting to touch home plate, I would not call the runner out for incidental contact by his teammates. However, if they would, for example, carry him off the field and he never attempts to touch home plate, I would call him out when he reaches the dugout area.
He's out. Missing any plate is an out. If the bases were loaded and the man on 2nd missed the plate you would only score a point for the man on 3rd (assuming he hits the plate). There would be one out if everyone made it to the home plate, but the man on 2nd, 1st and batter would not get runs.
If there are less than two outs, yes. If there are two outs, this is a timing play. If the runner crosses home plate before the batter is thrown out at second base, the run counts. If the batter is thrown out at second base before the runner crosses home plate, the run does not count.