Change jobs based on receipt number alone

My employer is has currently filed for my extension and I got the receipt number for it. Now they want to do it on premium for some reason. My questions are around how this affects my job hopping prospects.

1.) Will I get a new receipt number after upgrading to premium processing or will it remain the same as it was in regular processing?

2.) If it changes can I get the new number based on earlier regular processed receipt number?

3.) Based on just the receipt number how do I get a copy of the i797 document ?

4.) Can I switch based on just the receipt number (if receipt number changes, can I use the old regular processing number)?

5.) Will the new employer need anything else besides receipt number?

1.) Will I get a new receipt number after upgrading to premium processing or will it remain the same as it was in regular processing? 2.) If it changes can I get the new number based on earlier regular processed receipt number?

No, it is the same receipt number3.) Based on just the receipt number how do I get a copy of the i797 document ?

You have to get it from your employer only. There is no way, you get it by yourself.4.) Can I switch based on just the receipt number (if receipt number changes, can I use the old regular processing number)? 5.) Will the new employer need anything else besides receipt number?

I believe they will ask for a copy of the receipt notice or approval notice.

after I posted this question I found out about FOIA http://h1bsupport.com/blog/71/h1b-foia-request-to-obtain-copies-of-immigration-records

There it says a copy of the I-129 petition is sent by the USCIS. Will that be sufficient then to change jobs?

Its a gray area. You can always try. The I-129 is the application form of you H1, it will a bundle of 20-30 pages with all your document copies. I doubt it would have the receipt number on it.

Ask your employer for the H1 approval notice. It is illegal for them to hold when you request them. Requests should be made to the employer in writing, so you have proof that you made requests. If they dont give them to you, I suggest that you talk to a lawyer and request using the legality of your request.

Please dont confront them, ask politely. That you may need it for visa stamp, as you plan to travel out of country on emergency in near future.