Basically the processes are those that have been used for 1000's of years. Components of the milk along with some bacterial species that are commonly found in milk can, under the right conditions, produce some or all of your products.
First off, the online article is completely wrong, milk can and does "rot" - introduce some fecal coliforms (e.g. from off the often unwashed udders; see page 2 in pdf here, and table p 13 and references therein for prevalence of contamination, see also here for more detailed information) and you will certainly know about it within a few hours at room temperature. You will know this also if you have ever come across an old container of milk full of lumps and a horrific smell. There is a reason why large scale dairy industry keeps the milk cold from milking the cows to delivery to the factory - it's to stop the milk going off. Always store your milk at fridge temperature to slow bacterial growth. Note that fermentation of the milk products into soured forms generally selects against pathogenic bacteria and often enables longer storage and greater food-safety because of this. However, never assume that it is safe for consumption just because you have fermented the milk to make a different product. Correct storage is incredibly important for food safety with milk products.
For any of the cultured products - yogurt, cheese, sour cream etc., it is best to add cultures of the specific type of bacterium associated with the product. This ensures that you have the right one in there and are less likely to waste your raw milk by having overgrowth of unwanted microorganisms, some of which may be pathogenic and can make you very sick. Do not rely on your sense of smell or taste to detect pathogens. Many do not produce smells or tastes and can have very high bacterial loads before you can detect them from taste/smell alone.
From milk, skim the fat that floats to the surface and you have cream. Take the cream and churn it and you will have butter - you need lots and lots of cream for this. Buttermilk is technically the water component left after you remove the butterfat from the cream, but you can also add cultures to this one to produce the soured version more commonly seen commercially today. Incidentally cultured butter is also a thing: see the Types section in the linked page for butter.
Sour cream is cream with some culture added, usually Lactobacillus species that produce acid to make the cream "sour" thereby precipitating a lot of the proteins in the cream and making it thick and creamy. The same process happens for milk to yogurt.
The rest of your list are generally made from milk, often whole milk, but not necessarily. The exact product depends on how long you ferment it and what you do with it once it is fermented (and usually what you inoculate it with, in the case of cheeses). From whole milk the easiest cheese you can make is essentially mozzarella. Mozzarella doesn't require fermentation, but does require rennet, which most cheeses use somewhere in the manufacturing process anyway. You can also make quark by heating soured milk (add acid - lemon juice or (white) vinegar, or ferment) and straining off the whey.
For yogurt, which then can be made into soft cheese, you can inoculate with any plain, unpasteurized yogurt from the local store. Incubate this in a warm place for a few hours and the yogurt will be ready. Incubate for a couple more to make it thicker. With thick yogurt, place it into a cheesecloth and strain overnight in a cool place to produce a soft cream cheese like product called yogurt cheese. Yogurt and yogurt cheese products are probably the easiest milk based processed products to generate for a beginner.
Harder cheeses take a bit of work and know-how - you need to know how to culture, add rennet, slice the curd, pack, store to mature etc to produce each one. There are many many varieties of cheese out there, each one is slightly different in production and often take specific bacterial species, and sometimes a milk from a specific type of animal (e.g goat cf. cow) or variety/breed of animals (e.g jersey milk cf. holstein/friesian milk) or pasture type to produce its distinctive flavour.
