back to Russia in October but trip to china July there are big gap can hold visa such a long time

Hi I am Sri Lanka citizen I am studying medicine in Russia for 5years.I planned to Transsiberia route with cover the Beijing. so have to Start the journey from Moscow ~Beijing~colombo.That is the route.I tried to go this year but Corona stop it.next year is my final year I now planned to go now July of 2021.I want single entry visa.I want to know can I apply it from Sri Lanka. The problem is I am back to Russia in October but trip to china July there are big gap can hold visa such a long time.I hope your help.thank you