When is a vector copied, when is a reference passed?

I'm working with a program that makes use of std::vector a lot. Also there are lots of allocations/deallocations taking place, billions of them, and I'm trying to avoid as many of them as possible. Since I'm relatively new to C++, I have a few questions regarding allocations taking place when using a vector (e.g. when adding elements to it). I'm on a Win7 64-bit machine, the program is 32-bit and I'm using the current version of MinGW-compilers.

I'd like to know, what happens in the following cases, i.e. if the vector is copied, passed as a reference, ...

1.

std::vector<T> fillVector() {
    std::vector<T> returnVector;
    ...
    return returnVector;
}

std::vector<T> myVector = fillVector();

2.

 std::vector<T>& fillVector() {
    std::vector<T>* returnVector = new std::vector<T>;
    ...
    return (*returnVector);
}

std::vector<T> myVector = fillVector();

3.

std::vector<T>* fillVector() {
    std::vector<T>* returnVector = new std::vector<T>;
    ...
    return returnVector;
}

std::vector<T>* myVector = fillVector();

And the following, different operations:

4.

std::vector<T> myVector1;
... (myVector1 being filled)
std::vector<T> myVector = myVector1;

5.

std::vector<T>* myVector1 = new std::vector<T>;
... (myVector1 being filled)
std::vector<T> myVector = (*myVector1);

Assuming I don't want to change the argument in myFunction/changes in to myVector in myFunction wouldn't hurt the rest of the program:

6.

void myFunction(std::vector<T> myParam) {
   ...
}

std::vector<T> myVector;
... (myVector being filled)
myFunction(myVector);

7.

void myFunction(st