If you came here in H4 and now got admission in school, which has offered you assistantship you will be OK. If you came here in F1 and then H4 or anyother visa and again want to go back to F1, you should have valid reasons to make your case. If you are just going to community college or expensive school without any assistantship, you might face some problem. If you want to go back nepal and visit family, then you go with your H4 visa and come here and then you can change F1. What is your situation?