Bro, There is no way you go can go outside US after your visa expires. The beauty of US system is you can stay here as long as it takes to complete your studies,even though your visa might have expired. Yes, make sure your I-20 is valid and you keep taking the minimum number of credits. The only time you can think of going back is when you have a different visa, like H1, which you can apply after you graduate or permanent residence (green card). I haven't heard anyone renew the student visa from outside US. So, don't ever do that mistake. Complete your education, get the OPT. Apply for H1, get it then go to Nepal. But if you ever leave the US with an expired visa, remember, you wont be allowed back.