Thanks for answering all this! To 1) Yes the person is still working for the sponsoring green card employer. May I add 5) green card application still pending

Thanks for answering all this! To 1) Yes the person is still working for the sponsoring green card employer. May I add 5) green card application still pending when getting married to a US citizen, then a few months after wedding getting response for application that it was denied. Can the person still apply for a green card through marriage even if they are married for a while without having applied right after?