It has keys, but no locks. It has space, but no room. You can enter, but can’t go inside. What is it?

Always beside my lifelong twin, together we cushion the places you've been. I sit when you do, the same as I rise. I blush when it's cold, and I clench with surprise. What am I?

If you say me out loud, I am a door. If you think of me, I bring imagery of a cute love. If you feel me, there may be butterflies in your tummy. If you remove my fourth letter, I become the animal that Bambi feels this for.

I'm rarely touched but often held. If you have wit, you'll use me well

I walk on legs yet smaller than sand, I live through fire, the sea, and the land, In endless sleep, survival is planned. What am I?