Applying VISA to parents Immediately after H1B transfer approved

[bvramesh219]

Hi,
We recently had a baby and I would like to sponsor VISA to my parents to visit their grand child. However my H1B VISA transfer in progress. My specific questions here are

1. Can I apply B2 VISA immediately after I see approved status in USCIS website or do I need to wait to get my I797-A?
2. While my parents going to interview do they carry copy of my I797-A as well along with other documents?

Please suggest

Thanks and Regards,
BV Ramesh Babu