Does this dress zip up in the back? The back isn't shown in the pictures. I really prefer dresses that are fully covered, so no open parts. I like my shoulders and back to be covered, similar to how it looks in the front. Also, is this a one-piece dress or two separate pieces? One more thing: I'm confident about my size, but if the dress doesn't fit, can I return it without any hassle, just as it arrived? Please get back to me as soon as possible. I'm getting ready for a wedding, and time is really important. Thank you.