I got legally married to a foreign spouse in 2021. I filed as "married filing separately" for years 2021 and 2022. She never got an ITIN, so I put "nonresident alien" in her SSN# box. Starting in 2023, I began taking the "married filing jointly" tax deduction in anticipation of her arrival. I have not filed my 2023 taxes yet but I did file an extension. She will likely arrive around May this year, and as soon as she arrives she will receive an SSN#. She still has no ITIN.
Yes, you may file jointly now if you wish. Here is the procedure for filing.
I believe i answered your questions but reach out if you have additional questions.