Now, we should talk about two different processes. One is REINSTATEMENT and another is CHANGE OF STATUS. If you were on F1 and got TPS and did not maintain F1 then you have to apply for the REINSTATEMENT. If you had F1 and got TPS then you traveled to Nepal with AP and came back then it will be CHANGE OF STATUS as you do not have F1 status in I94 anymore.Check your current I94 so you will know your D/S. If your D/S is F1 go for the reinstatement, if something else then go for COS. One more think, you can not back to any previous non immigrant status automatically if you have not maintained that status so far. I hope this information helps. Your DSO can help in this matter!