I don't understand why 'imagine' has to show bank details and all stuffs posted above. Since imagine is calling parents in his/her graduation, parents should have sufficient documents to show that they are returning back to Nepal. All I had sent was:
1) transcript from last semester
2) graduation application
3) letter acknowledging from the department which said I was studying, graduating at that time and requested visa to my parents [my school didn't issue invitation letter because DHS has said to stop issuing such letters to international office].