1) The fastest way to travel the same plane
2) The most convenient is becouse the car can at any moment stop and walk.
3) The cheapest way to travel in the train
4) То же что и второй вопрос, только там комфортным а в 4 наиболиее комфортным.
5) The most interesting is the journey by car, becouse you can see everything uu window and go to look