PL SUGGEST BEST TOUR OPERATORS FROM INDIA TO CHINA & HONG KONG

Well, about the sightseeing in HK, to be honest, it is an international metropolis with modern transportations to be easily accessed, and also English is widely used, so it is quite convenient to find the way to your destinations. There's no need to have a guide.
About the tour in mainland, TravelChinaGuide is highly recommended. They have professional English speaking tour guides. And they can help you arrange the tour. If interested, the contact information is traveltravelchinaguide.com.