I'd the stadium underground?

Part of it.

Yes. The field and like 3 seating tiers are below ground level ; >

About half of it. When you walk in, you are walking into mid level.

100 feet embedded into ground due to airplane regulation

No

No it is not

Is not

Kinda.. But top level is at parking level

some but no

No as you enter the stadium you actually enter the middle of the stadium

No. The field is below the entrance level, but not underground.