wrong EB category

[boilerl]

I started my GC application early this year. I meet all the requirement for EB2, but there was some mistake in the minimum job requirement, and I was put in EB3. I am still waiting for my labor certificate to be approved.
1. Is it possible to change my category to EB2 from second stage, I140, or do I have to re-file LC?
2. Any suggestions whether I should continue with EB3, or change it to EB2(mainland born)?

Thanks.