My spouse qualifies as a resident alien. She does not have an ITIN, and we are about to file for her green card. Can we file Married Filing Jointly?

She may not receive her SSN through green card application for many months, so an extension may not be sufficient if we want to wait for it. Also, Turbo Tax is suggesting that we could be eligible to receive an additional $1400 because my wife did not receive the 3rd stimulus check. Is this true?