Can you buy tickets at the entrance?

Yes

Yes you can buy at the entrance

Yes, but is best if you buy it in advance on internet, because that's the only way you can know about discounts in certain days.

Yes tickets at the gate large lockers are $ 8 med are $5 sm are $ 4 tickets when I purchased mine was $16 if on line cheaper

Yes, it was $13 I think early in the day with a $5 locker key deposit for a large locker