[Number4]

To explain the stamina difference between starters and relievers:

Relievers are giving it all. Starters do hold just a little bit back, allowing them to work for a much longer time. However they do need to regenerate more, usually 4 rest days between starts.

After a reliever "sprints", he just needs to catch his breath a bit. He might be ready the next day if needed and the amount of pitches thrown (the "distance ran" so to speak) was low, but cannot go on daily all the time.

The starter runs long distance, but after the race, he does not need to get his breath, he needs a proper rest and regenration.

All in all, a starter works much more innings than a reliever, so the best pitchers become starters. However, they need to have either 3 solid pitches or a knuckleball in addition to stamina and just being good.