The 4X just refers to how finely the sugar has been ground. For example 10X sugar is powdered or confectioners sugar. The larger the number the finer the grind.
The main distinguishing feature of confectioners' sugar is that its a very fine powder (while regular sugar is often in powder form, it is more granular, hence the name granulated). This helps the confectioners' sugar dissolve faster, which may aid in some applications.
Yes
about 2
10X refers to the number of times the sugar is processed to produce fine powder.
That is about 2.2 cups
Yes, 10x sugar is a refined form of sucrose where the sugar crystals are ground into a fine powder. It is not considered one of the purest forms of sucrose as it typically contains a small amount of cornstarch to prevent clumping.
That depends on which Walmart you regularly shop at, but all in all they do.
You can, it's just not marked as such. Basic powdered or confectioner's sugar unless it is marked 10x is the same as 4x powdered sugar.
It is a reference to the fineness of the grain size. The bigger the number the finer the grain, eg:10X is finer than 4X. I believe that 14X is as high as it goes, though I'm not 100% sure. This fineness rating is generally irrelevant to the home baker. In fact, most icing sugar in grocery stores doesn't display it's fineness rating. If you're making whipped cream and you can find different grades pick up the finest one, it will dissolve easiest, giving you silky smooth whipped cream! :)
10x - 5x + 5x = 10x
That would be about 3 1/4 to 3 3/4 cups, sifted. The grade of sugar 10X or 4X will make a very slight difference and moisture will make a bigger difference.