
Not all open shows will put a running order up till the entries are in - to arrange the running order when you know the numbers involved makes better use of the rings and avoids (if it is done with care) the empty ring when there are still breeds to be judged.
To try to be concise: - A puppy that has competed and remained unbeaten by any other puppy may enter the Group/BPIS
If you enter a breed class and you are present you can not withdraw in order to remain unbeaten, if entered in the breed class you must do it. However if you win the breed best puppy you can withdraw from remaining classes.
I have known AV Puppy to be held as the first class and if you win that and still have the breed class to go you will have to win breed as well or you will not be unbeaten.
So a puppy may be entered in any class at all and providing you remain unbeaten by another pup you can go forward to group or BPIS
Of course, if the show is judged on a group system it will be group if not BPIS
When training a puppy for the ring I think to enter under different judges is a good idea but to worry about the group or BPIS can make your training program difficult to accomplish as you are worrying about being beaten rather that having a good time with the pup and making sure that enjoyment for the pup is paramount and withdrawing if the pup becomes tired.