1. its center; its origin.
2. not found (or eaten) in the West; i.e., rare animals and insects, rare herbs, etc.
3. Even if the dish seems unappetizing, try it. You may like it!
4. Presentation is everything. The color of the food, its texture, and how different foods are arranged together on the same plate or on various plates are just as important as how the food tastes.
5. "delight" means, take great pleasure in; "subject matter" means, well, given the context is about Chinese food I'd say the subject matter is the food itself.
6. You're right. But, not "can only"; try e.g., "will only mention a few in order to save time and space."