I haven't finished college without a high school diploma. How can I go to college now?
Schools are all about academic qualifications. You can go to college only after graduating from high school, and you can go to graduate school only after graduating from undergraduate course. The only person who doesn't speak academic qualifications may be a self-taught candidate. You try your luck. Go to the Beijing Self-taught Examination Office for consultation. In your case, can you sign up for the self-study exam? If you graduate from the self-taught undergraduate course, you can still go to Tsinghua to study as a graduate student at Peking University.