Rarely unless they have tp
No. You could do with an army.
Sometimes, although it will be another driver that they want to put there working hours down so they don’t have to give paid time off for working over your set hours.
Sometimes when routes are huge and especially heavy!
On specific routes with limited time windows for parking such as central Oxford and some central London routes. If you're given a particularly heavy day you MIGHT get given a mate but most of the time you're on your own