It's a terrible idea and it will not speed anything up to file an i-130 in advance, when a person is eligible to adjust as soon as they arrive in...

You can check the processing times at USCIS.GOV.

I am not aware of anyone doing this yet, but if you could get it done, it would be great!

No, a dependent's violation of status does not violate the principal's status.

You send it to USCIS initially. There is a complex procedure you should research.

You can remain in your country until the visa expires.

There is no requirement to be in the U.S. for an employer to file a PERM or I-140 for a foreign national.

Shortly in this context does not actually mean anything.

Yes, you can travel to the U.S. with an unexpired i-551 stamp.

It depends on what you mean by "valid". The receipt is indeed a receipt. It may not be sufficient for you to get new employment, for example, or...