L1 to H1 - Out of status

[visacheck1]

One of my friends has resigned from his L1 job and waiting for his H1 approval. There are 3 weeks gap between his last date with L1 employer and H1 approval date.
1) Is he out of status during these 3 weeks?
2) What will be the consequences if he stays in US for 3 weeks and starts working on H1 after approval?
3) How soon the L1 employer can revoke his L1 Visa?

[kabkaba]

If change of status receipt date is before the last day of work, it is fine. If not he is out of status.
After change of status is approved, he must start working for H1 employer immediately.

[visacheck1]

No, his change of status receipt is expected on Oct 28 and his last date of L1 employment was Oct 10. I think he is out status between oct 11 to oct 28. Is this correct?
Now will there be any consequences of this stay?

[kabkaba]

Yes, that makes him out of status. First consequence is that the change of status part of the H1 petition may get denied. If that happens he will have to leave the US and return with H1 Visa. The out of status period will affect all future petitions.

[visacheck1]

Thanks Kabkaba.
Can he work for H1 employer when his petition approval is in process? he has already started working for H1 employer although the expected change of status receipt is by Oct 28.

[kabkaba]

That is not allowed. In case of change of status he must wait until receiving approval with a new I-94. Even in case of H1 to H1 transfer, one has to wait for the receipt.

[visacheck1]

hypothetical question - How will the USCIS know if he works for L1 employer or H1 employer?

[kabkaba]

It can come up in any future petitions/applications.

[visacheck1]

can we safely assume that there is no problem for this petition then?