css all divs vs direct child divs

Answer 1

Actually I was searching this:

Selects the divs that are direct children of Root:

.Root > div {
    border: 1px solid red;
}

Selects all the divs under Root:

.Root div {
    color:green;
}

Answer 2

.root {
border: 1px solid green;
}

Why are you not declaring class /id for other divs?

Answer 3

Something like this?

.Root > :first-child, .Root > :last-child { border: 1px solid red }
.Root { color: green; }

Demo: http://jsfiddle.net/karim79/N5qFu/1/

I would advise you to go through this: http://www.w3.org/TR/css3-selectors/