Can I travel to Hong Kong without a Hong Kong license plate?

You can't. Vehicles entering Hong Kong must hold relevant certificates. Dual brands (Mainland and Hong Kong dual brands) or Hong Kong brands. There are also requirements for driver's license (because vehicles in Hong Kong drive in the opposite direction to ours, and all drive on the left).

In addition, there are parking lots near most Hong Kong passes for self-driving tourists to park their cars and enter Hong Kong on foot.