If you have illegal work experience and disclosed on I-486 (IR-1) pending..

Being married to citizen you will be forgiven for unauthorized employment.

What to do if I accidentally worked while waiting for my green card?

File and pay taxes. Your green card will be approved - they will forgive someone married to a US Citizen who worked illegally.

I485, part 8 item 15. Have you ever been denied a visa to the United States?

Thats a denied peititon by Immigration not a denied visa by State Department .

You can stay 1 minth and you cant ask for EOS - extension of stay COS - change of status or AOS - adjustment of status to green card.

How is CSPA age calculated for an F4 derivative? what will my CSPA age be in this case?

No you get til 12/24 2021 plus the 10 months it took them to adjudicate so about Oct 2022

Can I apply for k1 fiance visa outside US?

Yes - outside US is the only place you can apply for a K-1

I765-eligibility category

The I-765 filed with the I-485 uses the caregory C9

Is there still a chance for the 2 other applicant to receive an interview invite for immigration?

Only if you qualify under the child status protection act. You must look at the dste of I-130’filing, the date of I-130 approval. Then add that...

F-1 student and green card application. Will there be an issue of preconceived intent?

An I-485 cant be filed until I-130 is approved and the F2b quota has been reached assuming you stay in status.

Sounds like you will be approved but you also need to be patient at least a month tonallow officer to do paperwork for card production.