Open and shut, beginning to end. Leaves to turn, spine to bend.

A thorned rose that never blooms, A legendary key no lock to open. Cities of buildings without any rooms, A calm, still and waveless ocean.

I wear a suit, but most of the time I'm faceless.

You might use me to make your bets less risky, or make a maze with me if you're feeling tricky, finally when mixed with a hog you'll find the result quite prickly. What am I?

One type of me marks the best one can be, another is a way to remember. There's also the one where a sharp thing will run, for sounds to soothe your temper.