These are very popular stones. 8" Dia-Sharps have a single grit per stone making them more expensive, but at 8" by 3" they are wider than the 8" DuoSharps, offering a good working surface. The 8" Dia-Sharp line also has the widest range of grits available from DMT, with extra extra coarse, medium extra fine and extra extra fine options not available in other sizes, so it is good line to consider. One coarse and one fine stone is a good starting point.
Don't know. Not sure that I really care, as these stones definitely did the job that was asked of them, and did it with ease, even for a beginner whetstone user. I'll probably stick with them, at least until I get a lot more experience. Though, I do see a 10,000 or higher grit stone in my immediate future - more to play around with, than a feeling of genuine need.
When a whetstone is used to cut metal, it acts like sandpaper by removing small particles of metal (aka “swarf”) with each pass of the blade over the stone. Therefore, whetstones with more coarse grits cut faster than those with finer grits and, at the same time, soft whetstones cut faster than hard whetstones because each pass of the blade over both types of whetstones not only removes fine particles of metal from the blade, it also removes fine particles from the surface of the whetstone (aka “slurry”) which continuously exposes new cutting crystals. However, if the swarf is allowed to build up on the surface of the whetstone during sharpening, it will clog the stone and drastically diminish its effectiveness. Therefore, some whetstones require water to lubricate the stone and suspend the swarf whereas, other whetstones require oil to lubricate the stone and suspend the swarf.
A: You can sharpen your knives by hand using a stone or you can use a manual powered 1-stage, 2-stage or 3-stage sharpener or you can use a multi-stage electric powered sharpener. The choice is yours. Many people prefer not just the affordability but the precise control they have with an oil or water stone. While others opt for the more predictable results they get from an electric powered sharpener. It’s really a matter of taste.
When you want to learn how to sharpen a pocket-knife on a sharpening stone, your pocket knife isn't going to get sharp in one stroke. You have to have at least a stone bar that's the minimum of 2x6 inches in measurement. In general, it'll help make the sharpening of the blade easier. When you sharpen it on a stone, you have the three main options: ceramic stones, whetstones, and diamond stones.
Be careful: Don’t move your fingers laterally along the edge, you’ll cut yourself. Feel for a rough area running from tip to heel. Again, it takes time to know what to expect because the best burr will be subtle. Just know that the bigger the burr, the more metal you are removing—more than necessary. Don’t worry, you won’t ruin the knife doing this. You’re learning here, and mistakes are part of the sharpening journey. Learn from them.
"Sharpening is like a hangover cure," says Laurie Timpson, founder of Savernake Knives in Wiltshire. "If there was a cure and you knew about it, I'd stay at your house, crash on your sofa and have whatever it was when I woke up. Everyone would have it and there'd be no discussion. Everybody says they've created a perfect sharpening technique, and they haven't." 
In addition, the most prized of the natural Japanese Water Stones are quarried in the Narutaki District north of Kyoto, Japan and are commonly available as either bench stones or pocket stones in grits ranging from 120 to 12,000. On the other hand, synthetic water stones are made from Aluminum Oxide and commonly available as either bench stones or pocket stones as well in grits ranging from 220 to 8,000 and, although this is the same abrasive material used to make India Oil Stones, the difference between the two is that the binder that holds the abrasive together enables Water Stones to be much softer than India Oil Stones which, in turn, promotes faster cutting because the worn abrasive material breaks away more quickly and is replaced with fresh, sharp, abrasive material more quickly. In addition, because water stones do not become glazed or loaded with swarf like oil stones can, new abrasive particles are constantly exposed as the stone wears so it continues to cut consistently. Plus, they can be lubricated effectively with water (rather than oil which can ruin some water stones) which combines with the fine particles of abrasive from the surface of the stone to form a slurry which polishes the bevel as the stone cuts. However, it should also be noted that Water Stones do become uneven significantly faster than other types of whetstones although, their softness does make them easier to true again.