Travelling to Guangzhou overland. I have visa to China, can i enter china from kodari?

Kodari is the only way to enter Tibet from Nepal, but you are required to get a Tibet Enter Permit in advance. Your China visa is helpful to handle the Tibet Travel Permit. But if your China visa is issued from Pakistan, you need to cancel it, and then apply for a fresh China visa at the Chinese Embassy, Katmandu, Nepal based on Tibet Travel Permit. So, if Tibet is not in your travel plan, you'd better change route or take flight to Guangzhou directly.