Few questions about animation

I have some questions about animations.
1. How are the animation sequences attached to the base model?
2. How do you put an animation on top of another? (legs using running animation while torso is using another animation for drawing a bow)
3. Do walking/running etc animations automatically loop smoothly?
4. How do you start animating even though your model is in a T pose? Do you just bend the arms back down?

 

1. usually are set in animator component
2. need upperBody mask
3. no, must set transitions
4. skeleton animations are rotations (of limbs, spine, shoulder joints). the hip bone's position can be animated (jumping, crouching, swimming etc)