Can you substitute wine for cooking sherry?
Yes, you can use a red wine (preferably one that's been opened and left out for a day or two).
Do you have to be 21 to buy cooking sherry?
Hi, and no, you don't have to be 21 in order to buy cooking sherry - it is because it has had salt added to it to make it unpalatable to drink. It is ot controlled by liquor control laws. Another example of this kind of loophole is mouthwash - some brands are 25% alcohol (that would be 50 proof if sold as a liquor) but because they are adulterated, they are not drunk by most people (except really desperate alcoholics) and thus there is no requirement to be 21 to buy mouthwash. Some cough medicines that can be purchased by anyone are close to 20 proof, too.
What's the difference between cooking sherry, dry sherry, and very dry sherry?
Taking the first question last: Sherry is not the same thing as rice wine. Sherry is (generally) grape wine that has been fortified with other liquors, such as brandy. Sherry, like all wines, is categorized by its sweetness. The sweeter the wine, the less "dry" it is. So, the difference between a "dry" sherry and a "very dry" sherry is that a very dry sherry is less sweet. Although sherry's shelf life is stabilized by the addition of the other alcohol, it still doesn't have much of a shelf life, so "cooking" sherry has salt and other additives to extend its shelf life. I don't recommend using cooking sherry. It is widely available, however, in grocery stores. You can buy a small bottle of sherry to use in your recipe from any decent liquor store and store in the fridge.
Can Sherry wine be used instead of red wine?
Here's the deal: Red wine means red wine. If you use any type of sherry, it will drastically change the taste. There is such a thing as red cooking wine, but from every cookbook and cooking show I've ever seen you should NEVER use red cooking wine -- virtually every cook and cookbook writer says red cooking wine is absolute garbage that is not good for anything. Apparently the rule of thumb is if you wouldn't drink it then you shouldn't cook with it.