I am doing my second marriage-based extension, and apparently it went all good. But I'm on that 30 day consideration period, and the passport stamp tells me to go back there in the first week of November.

 

However, I just had the opportunity of making a month-long trip starting next week. The question is: Is that stamp day mandatory/unchangeable? Can I get a re-entry and then get my 1-year extension after I come back? 

A re-entry permit will only be valid to the date on the "under consideration" stamp. 

 

You would be wise to ensure you are able to return for your extension stamp on the day indicated.

You have to be here on the report back date or you will loose your extension application and will only get a 30 day visa exempt entry.

You can get a re-entry permit that will be valid to the report date.