I have keys but open no locks. I have space but no room. You can enter, but you can’t go outside. What am I?

Beneath the earth I grow, a humble brown knight. Though my visage is plain, I transform into golden delights or a comforting mash. From famine's grip, I once saved a nation.

I rest in a basket, shiny and round, With a crisp little snap when I’m bitten, I’m found. I can tempt both the wise and the bold, In stories of secrets and knowledge of old. From orchard to classroom, I’m simple and sweet, A symbol of health and a daily-time treat.

In yon chamber, a keeper of lore, Holds memories of miles, stored. A tarsal’s friend it dost be, Yet it holds not the knee, 'Tis a vessel where loafers are received.

Though she may be the lone stand on the beach Her stock is always at an arms reach If she ever needs some more She may always check the seashore