Yes, sugar is Kosher.
Everything that grows from the ground is kosher. There's nothing in sugar
to make it non-kosher, as long as it doesn't come in contact with other
ingredients, or machinery, used in non-kosher products.
Normal sugar is kosher.
This makes no sense. Some kosher what?
The question makes no sense. Who is "kosher"?
Lemonade is made of lemon juice, sugar, and water all of which are Kosher.
Any relation
Kosher Pizza Express
You need to call your local Orthodox rabbi so he can come to your house to help you.
That depends on the company that makes it.
flakes
All salt is kosher. "Kosher salt" is a particular grade of salt, with coarse crystals, that is used for making meat kosher, and is also useful in cooking. It's no more kosher than any other kind of salt.
Usually, provided that it contains nothing but fruit and sugar. If it contains grape juice, carmine, or gelatin it's probably not kosher.
If the kosher caterer in question makes wedding cakes, the cakes in question would be kosher.