Do I need an expansion gap around border.
If the border is glued and nailed, and the field is nailed, I imagine the field would push into the border and buckle.
Or do you only use glue for the entire and only use tongue and groove border nailed when the field is nailed?
Thank you.

I always leave an expansion gap at the walls. The flooring in the field may expand and cause some cupping but will buckle and come up only with extra moisture like a water spill that soaks in without drying. To keep cupping to a minimum the flooring ought to be acclimated before installation to the middle of expected seasonal humidity depending on where you live.