If there's no powdered sugar, can I use white sugar?

The stencils will disrupt the icing - refrigerate for about half an hour to 45 minutes and then use the stencils.

No, you don't have to use powdered detergent. You can use liquid detergent too, but powered detergent will make the process more efficient.

No. Powdered milk is dry, and milk is wet. If you add milk to it, it will get soggier.

Start with one tablespoon and add a second if you want. Whipped cream just makes it thicker and creamier.

If you are using milk paint on drywall, you may want to add an acrylic binder to the first layer for a more opaque finish.

You can just take regular sugar and put it in the blender, and blend it until the sugar becomes a powder.

You could, but you would be disappointed in its flavor. It will not be a sweet as you are expecting.