There may be provision to have a call to discuss the work, or it may purely be the delivery of a structural report or a line edit or proofread manuscript. I've worked with professional editors for the last ten years and have never had a call to discuss, but if you're the type of person who wants that, then make sure you put that into the contract upfront along with anything else you are concerned about.
After researching a lot of different designers, I went with Ebook Launch for my debut novel because there wasn't a single cover in their portfolio I didn't like. I didn't know exactly what I wanted, but I knew what I liked and what I didn't like, and they took my mishmash of half-formed ideas and turned it into a beautiful, eye-catching, genre-appropriate design! Not only that, but they were speedy, responsive, and accessible. A real pleasure to work with. I will definitely be coming back to them for the rest of the covers in the series.
Developmental editing (may also be called structural or content) – looks at the book’s big picture and overall structure in nonfiction or plot and characters in fiction. Developmental editors may assess a book idea, outline, or early draft to tell authors what works and what could be better. The big picture questions need to be answered first before an editor ensures your words are polished and used correctly.
As a freelance editor, I would like to express my strong disagreement with the idea that a freelance editor must work as an employee of a publisher for three years to be any good. In my field, spirituality, many publishers have gone to having most editorial tasks beyond acquisitions performed by freelancers, so the in-house positions being held out here as a prerequisite for freelancing simply don’t exist; many editors must cut our teeth as freelancers. It also occurs to me that self-published authors usually bristle at the idea that they are not “real” authors unless their work is accepted by a commercial publishing house. Is it fair to apply this standard to the people they propose to employ as editors?

The job board is NOT a big reason to join the Den, especially if you’re a new writer. It’s a higher-end board that doesn’t post any low-priced gigs, and is a good resource for mid-career writers. But in general, the board is a real sidelight to the point of joining the Den, which is to access 300 hours of training+, 24/7 forums for support, live events where you can ask questions of experts, and more.
Regarding your last question, I know of no editor who gives a money-back guarantee for occasional errors that happen to slip through or for a different opinion by a later editor. I’m afraid such things are just the nature of the publishing beast. But by having a shorter portion edited first, you will get a decent feel for whether someone is the right editor for you, and will be able to be confident in his or her work on your entire book.