Yes! Just use kosher fish with fins and scales and do not use any kind of shellfish or mollusks.
No.
Make sure all of the ingredients are kosher and the utensils and kitchen it's being prepared in are also kosher.
No, but there are kosher companies that make spices. Just look for the kosher symbols on the products.
If the kosher caterer in question makes wedding cakes, the cakes in question would be kosher.
In order to make kosher gourmet bread, all of the ingredients would have to be certified kosher and the bread itself must be prepared in a kosher kitchen following the laws of kashrut (Jewish dietary laws).
Some kosher companies make cereals that are Kosher for Passover.
Kosher food refers to foods that are prepared and consumed following the laws of kashrut (Jewish dietary law), it is not a style of cooking. That being said, it's possible to make kosher versions of dishes from pretty much every country, this would require a kosher kitchen and kosher ingredients. Without a kosher kitchen, it is impossible to make kosher food.
Kosher salt is sodium chloride.
All salt is kosher unless something is added to it to make it not kosher. Like all other seasonings, the specific package must be certified kosher for Passover.
When it comes to kashrut, food is either kosher or not, there's no inbetween. In regard to making a kosher salami, it must be prepared in a kosher facility with all kosher ingredients including the meat, spices, and casing.
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.
All plants are considered kosher. They need to be washed thoroughly, (especially leafy vegetables,) to make sure there are no insects on them which would render them non-kosher.