I'm planning to go to China from Hong Kong and apply for a double entry Visa

because I also want to visit Taiwan. Do I need to provide an itinerary for the first 30 days or also for the second 30 days after I come back to China from Taiwan? If so, do I also need to show bookings for after the second entry? Do I also need to show 2 tickets out of China? (one to Taiwan, and one at the end of my visa?).

Thank you!
Bart