All u need to show is your flight tickets, even if its open end ticket. There is no need to show your hotel bookings. The number of stay is usually 30-60 days per entry. It will be stated in your visa. If you need extension, you can do it in China itself by visiting the nearest Public Security Bureau (something like Police Station). They will give a 1 month extension. If you need 6 month stay, best you do it in Hong Kong, and the visa is just a stamp and is ready within a day for a price of course. I did my backpacking across China twice 6 years ago. Fantastic.