If that photo is representative of the area in question, then I'd reconsider using this extremely tight space for "outdoor living". And unless I am missing something, that slope is not very severe. Even if leveled, I doubt this area would be congenial to lounging outdoors or utilizing as a patio, etc. Too exposed and too restrictive and without sufficient space to develop any kind of green privacy screening. I'd consider just a mixed shrub buffer between you and the neighboring property, perhaps with a meandering pathway connecting it to more usable areas of your property. Unless that photo doesn't reveal the true slope of the area, I'd say no terracing or retaining walls are necessary or even practical. Can you post photos of other areas of your garden that may be more conducive to outdoor living/entertaining? I still think this is a situation where engaging a professional for an hour or two can be helpful - it is difficult even from the photo to get a good visual and a true sense of exactly what you are dealing with.

Do you have a basement? Do you have some particular worry about the drainage around the foundation, i.e. some ongoing issues? Basically I would separate these issues and not think that adding a lot to your yard is going to magically fix the issue. The house probably should have had some kind of drainage (like French drains) around the foundation to deal with regular rain. "Flooding" could be a number of things but if it's the water table coming up too high, a yard that drains somewhat better isn't going to make that big a difference. So if that's your concern and you're really worried about it, consult a professional. You'll also want to look at your drainspouts and that they lead the right way. As far as amending soil for the garden part, if you really want to level things out it's going to mean adding a lot of organic material. This is going to depend what's available in your area, but wood waste, wood chips and wood in bulk are likely to be the cheapest. You may find local utilities (that clear wood trimmings around lines) may give away free. You can bury wood (hegelkultur) and add wood trimmings and chips either in ground or above ground. You'll likely have to repeat several times (the wood - any organic matter - will decompose and shrink over time). You'll hear that wood waste dug into soil may 'lock up' nitrogen for a while and make it harder to grow a garden - but over time the nitrogen returns to availability in the soil. It may take a few years but should eventually create a good garden soil. So partly depends on how big a hurry you are in. You can also do the way you propose it will likely just require a _lot_ of material. There's nothing wrong with doing a combination, either - all of the stuff will help. Sand is probably a bad idea. The more organic material, the more chance the soil biology will do some of the mixing for you. I'm mainly suggesting wood of various kinds as most likely available in very large amounts. As I said - the organic material/better soil won't magically solve drainage issues. It will help buffer rainfall some - less likelihood of pooling of water or standing puddles - but within limits if the soil deep down is all clay and/or the water table rises too high. This is pretty generic info - don't know anything about how bad your clay is (if you search here, you'll see lots of people have thick heavy clay soil problems), very little about how bad your flooding issues are, house construction, etc. There are more serious solutions to drainage and lots of info about ways to help, use Der Google. )

Since no planting can be figured out until the hardscape is planned, you should limit your request for help to hardscape to start with. It's going to be hard to help with hardscape until you can make the site and your expectations better understood. Will there be walks that link various doors? These should be made obvious on the plan. Would the larger patio be adjacent to the deck? Is this the front yard or the back? Do guests enter the property through this yard? Is that the permanent location of the hot tub? You didn't mention a fence around the carport. Is that a passing thought or something you're committing to? It's important to stay at a single position with the camera while capturing a view. I would suggest you show us the yard from this view (see plan) providing a full 180* of slightly overlapping pictures. Because the area is at a lower level, it would be best if you found something 2 or 3 feet high to stand on for the pictures, and hold the camera in the vertical format. If possible, set the pictures to a size or two up from what you're showing above, as those are small. The above pictures might have loaded sideways if you're uploading them from a phone. Try submitting new pictures via computer.

Apple pollination is a lot more complicated than "Pollination happens as long as bees can fly from one tree to another of the same type." In fact, an apple of the same type may well be a poor pollination partner. "To ensure good pollination and therefore a good crop, it is essential to grow two or more different cultivars from the same Flowering Group or adjacent Flowering Groups. Some cultivars are triploid – they have sterile pollen and need two other cultivars for good pollination; therefore, always grow at least two other non- triploid cultivars with each" https://www.rhs.org.uk/advice/pdfs/applepollinationgroups.pdf You also need to be careful with Vinca major and minor. They're invasive species in much of the US.