I am a Taiwanese citizen who originally entered the US in 1995 with B-2 visa and then was able to changed to F-1 status. I have maintained my student status throughout my stay in the US until 2012, then I got a job and then switched to H1b status. I have never left the US except only traveled to Canada once in 2001 and was able to come back using automatic revalidation. I am planning on going to Canada again soon for a conference, will I have trouble coming back to US using automatic revalidation? The thing I am worried about is that I have an expired B-2 visa, and changed my status twice (to F-1 and then H1B status again) without going back to Taiwan to renew visa. Can they randomly reject my entry?
Another question, I am not planning to renew my H1b visa at Canada. I know that I will not be able to return to US with automatic revalidation if my visa application gets rejected. But, if I do apply, what's my chance of getting it approved there (as a third country visa) since H1b is a dual-intent visa status? Please help!! Thanks in advance!!

