Riddled

It's been a while since I've posted here, but I thought I would add a few riddles I have come up with lately... here ya go...

I have experienced many twists and turns in my lifetime, but have gone through only one door. What am I?

 I like to follow most of the time,
But once in a while I lead,
And when I do
You'll find out who
Can clone me with great speed
What am I?

 I run but don't walk,
Breathe but don't talk,
I'm found in a litter
But not in a flock.
I do not have wings, or arms, or a tail
But yes, I have skin, and sometimes I smell
What am I?