l come in through Hong Kong and exit through Beijing. I have hotel reserved in Hong Kong. Is that OK

You are exempted for visa in HK. So you should apply one for mainland China. You need to provide round-trip air tickets and hotel booking in mainland China instead of HK, I think. By the way, if you can acquire an invitation letter from a Chinese citizen in PRC or a friend of yours there, you needn't provide the air tickets and hotel reservation.