I changed my status from F1 to H1B in US and has no H1B visa stamp on the passport, instead I have only I-797A approval letter. I traveled to Canada and Mexico for conference and got seal on the passport to show the entry date under H1B status. Is my status of last entry in F1 or H1B? If I put H1B, how should I fill in the visa # and consulate where the visa is issued, since I don't have it at all. Most recently I traveled to Canada by car. I got a seal on the passport to show the entry into Canada, and no seal to show the reentry to US. Is it counted as my last entry to US? Thank you!