New Employment - I-797 & I-140 status

[skrish80]

Hello All,

I have a situation (as explained below) for which I am in urgent need of your suggestion!

My Case
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I have an approved I-140 through company A while working in US and due to personal reasons I had to return back to India during 2016.

I have been working for the same Company A in their Offshore Development Center in India.

Also Company A had informed me that as a standard practice they don't revoke approved I-140, since its meant for future employment.

I now have received an offer from Company B.

I am planning to stay in India for couple more years and consider travelling back to US whenever required after couple of years.


Questions
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1.Can company B now file for new I-797 using the approved I-140 of Company A (Assuming the Company A didn't cancel the approved I-140)? Also my current I-797 got

expired in 2016.

2.Is it a good idea to transfer the I-140 through Company B immediately (after applying for PERM and Labor through Company B) or

to wait for it until the time comes to apply for I-485 (which is like 4 or 5 Yrs away from now) ?

3.Can I now travel to US, if I-140 is through Company A and I-797 is through Company B? Will there be any implications in Port Of Entry?

Thanks in advance!