Recently (2009), I changed my status from H1B to H4. My Employer cancelled the H1B after I changed the status to H4 Visa. I have H1B petition document(I-797) with me. 1)Now Can I use existing H1B with the new employer? 2)Do I fall under quota or I need to file new H1B in this Year quota?
You will be exempt from the quota (assuming your previous employer was a private employer - NOT exempt from quota). The new employer will need to apply for an H-1 again.