Yes, I think this is the better way to ask for a phone number: 你的电话号码是什么? "What is your phone number" versus the example/answer given ~是多少?which is like asking "How many~". Can any native speaker enlighten us, please?
香港 describes/modifies 电话号码, so it has to come first. That's just how the word order works in Chinese, at least, in a simple sentence structure like this. This is my understanding. I'm not a native Chinese speaker.