1.)I'm trying to write code to swap element  and element  in an array of floats called ARR. I need to declare a simple variable called temp for this question, and assume the array is correctly declared and initialized.
2.)Also how would I write code to copy the 0th element of an array called ARR into all the other elements of the array assuming there are 10 elements in the array.
Sounds easy to me. You even explained how to accomplish #1 so you already know how to do it. However, you can let the STL do the work for you. Take a look at the swap, fill, and fill_n algorithms. http://www.cplusplus.com/reference/algorithm/