Can evaporated milk be converted to "regular" milk?

Yes, you could certainly reconstitute evaporated milk by adding water.

The outcome would give you similar but not identical results as fresh milk, due to the change in flavor the milk underwent while being cooked down to the evaporated state: it will retain the slightly cooked, caramelized flavor. This may or many not have a significant effect on a given recipe.

Milk also freezes, and still is suitable for most cooking purposes, should you choose to do so.

Finally, if you use milk very rarely, unless you are making a dairy dominated recipe like custard or cream soup, you may not have to use milk at all. Water or another liquid might perform similarly or well enough—it depends on the specific application.

Yes, evaporated milk can be reconstituted to regular milk consistency. The correct ratio is 1 part evaporated milk to 1 part water (ref. one manufacturer's FAQs) (e.g., if the recipe calls for 1 cup milk, use 1/2 cup evaporated milk and 1/2 cup water).

I've frequently used evaporated milk in both savory and sweet recipes, both diluted and not. (Indeed, diluting a bit less than 1:1 can provide a creamier consistency without needing actual cream. Whether that's desired depends heavily on the recipe, though.)

Evaporated milk is only slightly sweeter than regular milk,* although it isn't heated for a long period of time. After pasteurization (a very brief heating process), the milk is reduced using vacuum evaporation (exposing a liquid to a pressure lower than atmospheric pressure to reduce its boiling point), and "as a result, the milk is concentrated to 30-40% solids ... [and] has little or no cooked flavor" (ref). Usually, the other flavors or seasoning in a recipe are more than enough to overwhelm the difference in taste between diluted evaporated milk and fresh milk.

* Note that this does not hold true for sweetened condensed milk, which has extra sugar added. Don't expect similar results if you dilute sweetened condensed milk.

I put 2-12 oz. cans of evaporated milk in a half gal jug and fill with water. Chill for a couple hours. Tastes great on cereal, coffee or after Peanut Butter and Jelly. Good yield at 1 to 2.5 ratio. Stores and travels well in can. Works just as good with ice and water on the go. Hardly use regular milk anymore.