When can a bracha carry over onto more food?

Question

If i make a bracha x, eat some y, then decide i want some z, do i need to make another bracha? I'll present a few cases for x, y, and z here.

1. Make a mezonot with the intention to eat one cookie, and then want another cookie from the table. (Same food, originally available.)
2. Make a mezonot with the intention to eat a cookie, and then want a piece of cake from the table. (Different food, same bracha, originally available.)
3. Make a mezonot with the intention to eat cookies on the table, and then someone brings out some more. (Same food, originally unavailable.)
4. Make a mezonot with the intention to eat cookies on the table, and then someone brings out cake. (Different food, same bracha, originally unavailable.)
5. Wash and say hamotzi, eat the meal, and then i discover that there's desert. (Ikar/tafel, originally unavailable.)

Answer 1

I will have to wait until tonight to cite my sources, but:

1) When one makes a bracha on some food, it is assumed to cover all foods with the same bracha that are on the table.

2) Same as 1

3) If you are eating at someone else's house, a bracha is assumed to cover all food of that bracha that is brought out. This is because a guest doesn't know what food will be brought, so he includes everything in his bracha by default.

4) Same as 3

5) In general, dessert is not considered a part of the same meal, and one couldn't even include it in his hamotzi if he knew it was coming. So the person would have to make a new bracha. The exception here is for certain mezonos foods that might be counted as something that could be eaten as part of the meal. There is some controversy about which foods are included in this list, so CYLOR but AFAIK, most halachic authorities include many kinds of cakes in this category.