Kalatta
Use AP to re-enter. Now at foreign consulates ( I know friends who are stuck in India for a month or so) it is taking time get security clearance for VISA stamp.
-Once can use AP to re-enter and maintain H1B status.
-It does not matter whether the H1B Visa stamp you have in PP is expired or not as long as you kave a valid H1-B for all the time.
An extension to that is, try to maintain H1B status as much as possible till you get your green (b'coz can bring spouse, change jobs without hassles of AC21 sometimes etc)
EmailRaja
Why do you want to go to canada for H1B. Most probably they will invalid your current stamp and ask you to get one in your home country.
If you have AP, use it.
PS: I am not a lawyer