EB3 Green Card

1. Absolutely fine. There is no law that states that in order to enjoy job portability you must necessarily use your EAD. In fact, in ninety nine percent of the cases I would advise you to transfer on H-1B simply because if there is a problem with your I-485 we are on solid footing to fight it out, otherwise you would be out of status and unlawfully present if your I-485 is denied. Hence definitely keep your H-1B active.
 
2. That depends. It doesn't have to be a one-on-one match job location. You can move from one state to another as this is a part of AC21 compensation. The only time you will have a problem is if the compensation is unexplained and it's a huge jump. Always ask an attorney who understands your situation to review your file. 
 

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Note: Unless the context shows otherwise, all answers here were provided by Rajiv and were compiled and reported by our editorial team from comments, blog and community calls on immigration.com. Where transcribed from audio/video, a verbatim transcript is provided. Therefore, it may not conform to the written grammatical or syntactical form.

1. The reply is “No”. They cannot because employer B’s EB-3 was inherited by employer C, and you never filed a I-485 so that cannot be used.

2. Either go back to the first employer if they have a job offer. You can actually apply for a I485 without joining but this should be discussed with your lawyers in detail. Hence you could file for a I-485 based upon the job offer and I-140 which was approved through employer A but if you want to stick with employer C either you stick with EB-3 or you start another PERM application through them for your EB-2 categorization.

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Note: Unless the context shows otherwise, all answers here were provided by Rajiv and were compiled and reported by our editorial team from comments, blog and community calls on immigration.com. Where transcribed from audio/video, a verbatim transcript is provided. Therefore, it may not conform to the written grammatical or syntactical form.

Since you have already entered and resumed the same job you are still considered to be on H-1B. There is nothing to get back to.
Yes, you can. Although you have traveled on advance parole you should be able to file EB-2 interfiling. 
For more information you can also visit my blog:
https://immigration.com/blogs/adjustment-status-transferring-basis-i-48…
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Note: Unless the context shows otherwise, all answers here were provided by Rajiv and were compiled and reported by our editorial team from comments, blog and community calls on immigration.com. Where transcribed from audio/video, a verbatim transcript is provided. Therefore, it may not conform to the written grammatical or syntactical form.

1. Sure. EAD allows you to work, but advanced parole allows you to come back.
2. The law is if you return to the same job that you were doing on H-1B even though you used your advance parole you are still considered to be on H-1B.
3.  I am assuming that the green card was filed by you and not your wife so the divorce has no effect on you.
4. I do not see any obvious violation of the law. I am just suspicious of that time you were on H-4/H-1 and had your own company. The only time you are completely free is when you were on H-4 EAD.

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Note: Unless the context shows otherwise, all answers here were provided by Rajiv and were compiled and reported by our editorial team from comments, blog and community calls on immigration.com. Where transcribed from audio/video, a verbatim transcript is provided. Therefore, it may not conform to the written grammatical or syntactical form.