Am I still a legal resident after my I-551 stamp expires?

No, you are still a PR but do not have evidence without the stamp. USCIS has indicated that is one of the exceptions that they are allowing INFOPASS appointments for so call the 800 number and advise you need to be able to continue to work and be paid.

You will continue to be a permanent resident until ordered removed by an immigration judge. The expiration of the temporary green card stamp, or of the conditional card, or even the denial of the I-829, do not automatically terminate your status as an immigrant.

You are still a legal resident. The stamp is merely evidence of that status. One thing to consider is filing a mandamus based on the long-pending I-829. Check out my analysis at: https://www.galati.law/post/covid-19-exacerbates-form-i-829-processing-pain-for-eb-5-investors-lawsuits-growing-in-popularity

Yes, still a resident. USCIS is reopening June 4. Call the 800 number and see if they will give you an infopass for the stamp.

Yes, you are still considered a conditional permanent resident. The standard practice is that your CPR status is extended while your I-829 is pending. Your boss needs to comply with the law and has no right to unilaterally declare you to be out of status. Advisably, contact an attorney for consultation and to intercede on your behalf.

You are still a conditional lawful permanent resident even though your I-551 stamp has expired. Unfortunately, it appears that USCIS is scheduling emergency InfoPass appointments for healthcare workers only. USCIS may reopen its offices to the public on June 4, so you could try calling USCIS again to schedule an appointment after that date, assuming they reopen to the public and the date is not pushed back further. As for your boss, technically he needs an updated document for I-9 purposes, either an I-797 extension notice or a new I-551 stamp. I do not think anyone would fault him or his company if they placed you on a temporary leave of absence (even with pay) during these extraordinary circumstances.

Yes, you are still a legal resident. Speak with your attorney about addressing this issue with your boss.

You can get a stamp, just call customer service. Check the I-9 instructions on the USCIS website. No, they are not allowed to re-verify your status.