Bravo ! Bravo! Bravo! Xinxinqui! Your son is a wonderful pianist!
I really enjoyed his Etudes by Chopin. They are extremely difficult in fingering. I tried to play the Etude #3 ( I think E major) - no problem with the slow part - a nice study in touch but the second theme is a real trial for chromatic passages. Your son did very well indeed. The second Etude your son played the #5 in G flat major is a real Chopin piece of genious. The left and right hands are talking to each other in nice replies. It is delightful to hear this vivace piece. I love the Beethoven piece too - the Moonlight Sonata. I guess you can only play two movements probably due to the competition rules. The last movement is nicely played with great fingering. I played it in my younger dates but I find the last movement very exerting for me especially when you have small hands. The octaves kill you.
Congratulations on your son's success. He is only 17 (right? Going to U next year) It takes great parents to nurture such success for your son. I hope to hear him play one day - the Pathetique, the Appassionata, the many beautiful tunes from Lizst and Chopin. Xinxinqui congratulations indeed!