IF your own company files for an extension while your I-94 is valid, you CAN continue working while the extension is pending. If you resign, you cannot work for another employer even if the I-94 is valid. You can remain in the US while the I-94 is valid and you will not be considered unlawfully present but you will be out of status and even if you find another employer, you will not be eligible for a change of status within the US but would have to go for consular processing abroad.
Answered on May 16th, 2013 at 7:43 AM