How long to wait before porting I-140

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Hi

I am in the 6th year of my H1-B under EB2 with a priority date of Feb 2012 and am have currently applied for my I-140 under premium processing. I am a mechanical engineer and currently work in Minneapolis, but am looking to move to California. I have two quick questions regarding same.

1) Do I have to wait 6 months after getting the I-140 to be able to carry over my priority date to the new employer or can I change jobs right after getting the I-140 and still keep the PD?

2) Since the wages will be considerably different between CA and MN, will that be taken in consideration during the reapplication of LCA or will the cost of living adjustment be considered?

Thank you all for the help!

VG