Can i visit great wall in late desc. (20-25th)? if not when is the good time to visit? How b,t Kunmg

Hi, I do not think it is a good idea to visit the Great Wall in late December. It will be very cold and sometimes, you may meet the snowy days. But if you want to see the snow espcailly, then it is a good time.
The best time for climbing is from April to late October.
About your last question, do you mean Kunming? If so, you can go there during Dec. 20-25. There you can enjoy yourself.