There are no limits on the entrance order--entrances can be repeated in the list (so things like "2, 1, 3, 3, 0, 1" are allowed), and there is no practical limit to the size of the list. If invalid indexes are in the list, then they're skipped as though they weren't even there (meaning that if there are three entrances and the list is "1, 3, 2, 0", then the list becomes "1, 2, 0"). The only other thing to keep in mind is that only non-fake entrances count, so if there are three entrances and the second one is fake, then the third entrance has an index of 1 rather than 2.