All the days of your life.
Yes and no. There are many recipes that can be made kosher with kosher substitutes.
Many major brands of mayo are kosher.
You would have to check the label for a reliable hechsher. These days, there are a good number of high quality kosher sparkling wines.
Many kosher kitchens are American.
There are many kosher symbols, many reliable, and many not. Take a look at http://crcweb.org/kosher/consumer/Agency_List.html The crc is chicago's main beis din and kashrus agency
Kosher cookies are cookies that have been made with kosher ingredients. For example, no gelatin from animal sources (so marshmallows must be kosher, which are made with fish or seaweed-based gelatin.)
Kosher ice cream can come in any flavor, there is practically a substitute for every food now a days. However, not everywhere that sells ice cream may have Kosher options. Your best bet is to ask someone who works there if they have any Kosher flavors.
Lots!
Anyone can eat kosher food. However, kashrut is a part of Judaism and religiously observant Jews will only eat kosher food. Kosher food is food prepared in accordance with Jewish Dietary Law. Many products sold in stores are certified kosher, so many times you will be eating kosher food without realising it. Kosher products are marked with a symbol that is associated with the organisation that provided the kashrut certification.
go to http://www.shamash.org/kosher/ and search for Madrid in Spain, that's all you need to know. but yes, in short, there are many restaurants.
Kosher refers to food that is prepared according to the laws of kashrut. The people who keep kosher are Jews. Kosher is a classification, not a people. That being said, if the nachos and salsa are certified kosher, religious Jews who keep kosher can eat them.
Yes, provided that only kosher ingredients are included in it, and that it's mixed and baked with kosher utensils.