I do not have the diamond elite pass, but I do know that 50% off is the minimum so other days it can be more or even free. I believe that for the 50% you can do multiple friends. If not then I do know you can use multiple discounts for ex: I used a bring a friend for 20$ and a bring a friend for 50% off on the same day.
Just one person...but you can use several time...so you can reserve for you and then tou can give the pass to another person. I had Platinum pass.
I believe it's just for one person, you should refer to the details found online
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