回複 換雇主的大問題.
1) Depends on what catergory your petition is. You are free to change employer if you are in EA or NIW, whereas you have to stay with your current employer until your GC is secured,if you are in OR, since OR has to be sponsored by employer.
2) Better to include your supervisor's letter for EA and NIW, yet it is not essential. On the other hand, you have to have recommendation from your employer as sponsor for your OR. Good luck.