Are there lockers to hold items?...so if you make purchases prior you won't have to hold them as you experience the exhibits

No, just bring a sturdy bag to carry your souvenirs comfortably. Or wait to buy them until the end of your visit.

Backpacks were a plenty.

No u have to carried a bagpack

No, but you can bring in a backpack

Didn't see any. Check their website to confirm