I can be a command for the military, an office or a thing in the ground. What am I?

I’m a very relaxed mollusk, that is until I get turned into chowder.

Your life in yours and mine in mine. Upon you sit, a shift in spine. Part for the mints. Part for borrowed lines. Forgot at home, virtual shines.

I'm Moby Dic's worst enemy, not Ishmael, but sinister indeed. From the bow, I enter thee, piercing deep, you'll come to me.

The British have bad ones, The old use fake, The young have none, You need these if you want to eat a steak! What am I?