do I need a stadium chair for my seat? Is there a back rest in the seats?

Definitely bring a blanket, it gets chilly. Also a chair cushion or two. Wooden chair can get a bit uncomfortable.

Depends on if you have a bad back or not. A seat pad is nice, you dont need back support and they do offer pads to rent if you wish.

There are back seats in the chairs, you will want to bring a blanket, it will get chilly