Urgent: Will F2 visa valid after changed to F1?

[Lwin]

I am currently staying in U.S with F2 visa and my husband is studying in U.S. Now, I also would like to study in U.S and I got I-20 from a university. But, I have to take an admission exam when I arrive to university after I have changed to F1 visa. If I fail that exam, I will not qualify to attend that university and my F1 visa will not valid. At that time, how can I stay in U.S? Can I stay in U.S with F2 visa if I fail the exam? Or Do I need to go back to my country to change F1 to F2 again? Please answer my question. I need your help.

[inadmissible]

You can apply for a change of status using Form I-539. If you live near the Canadian or Mexican border, it might be cheaper for you to just take a daytrip abroad and return