Working in Korea for 2 years, interested in multiple short tourist trips to China while here

I'm a female professor working for 2 years in Korea and would like to while here be able to do a few short weekend trips for tourism to China. I'm still unsure of my travel dates, and would like to travel spontaneously ('not a lot of grading to do this weekend, I think I'll get a cheap ticket and pop over to Shanghai this weekend for better food and shopping'). But to do that I first need a visa.

I'm looking at the website and it says I can get a one year multiple visit visa, but that I have to already have a hotel reservation and ticket booked before I can get it. Is that true? Can I just get the visa and then travel when I feel like it, or do I have to have travel booked before I can get the visa?

Also, is Hong Kong part of the visa or for them do I need something different (I also want to go to Disneyland).