Is after the Waiter seated a CustomerGroup this waiter locked and only he can take Orders,serve Meals and Escort this particular Group or is it also possible that one Waiter seated a group and another serve this group?
Seating a group is euqal to assigning the waiter to the group. So this waiter will always take orders, serve and escort this group
Seems to be the case, page 14 lines 16-18:
For both REGULAR and CASUAL groups, the selected waiter is assigned to the group and table and will be responsible for all further actions.