On a plateau of keys, when things go wrong, im probably the first key you try to leave. No need for control, alternatives and deleting things if this key works

Trains follow me both night and day, though I myself don’t move or stray.

Poor people have me, rich people need me, and if you eat me, you'll die. What am I?

I stand alone in endless blue, Yet never sink, though waters strew. I bear no bridge, yet host the ground Tell me, traveler, what you’ve found?

A wand. A water. A hand. What connects us? One word can. Flourish, roll, or side to side. A waxy board is fit to ride.