Immigration Site

I have a question about a mix of visas... I am a Canadian citizen born in India. Right now Im working in the US. My employer has filed for my Green Card and my I-140 has been approved but since my priority date is from 2008 I dont expect the process to complete any time soon. My H-1B already ran its six year course and Im now on a 3 year extension. Now I want to do an MBA and Im considering schools in US, Canada and Europe. But here are the questions:

1. Would I be able to get an F1 in the US considering that I have my I-140 approved? Im assuming this would abandon my green card application but Im wondering if Ill have trouble getting the F1.
2. Once I complete the MBA (either from a US school if I get the F1 or from somewhere else), would I be able to get an H1 again if I wanted to work in the US again after that?
3. Would my abandoned Green Card application be a hindrance to me entering the US again, either on an H1 or just for visiting?

Thanks for your help.