Q: I'm a green card holder and started filling out the N400 form for citizenship. My green card expires 2/2020.

A: I recommend you complete the N-400 and then also file an I-90 to renew the green card. You remain a permanent resident regardless of whether your green card is expired or not, but obviously an expired green card can make it difficult to get work, renew driver's licenses, travel abroad, etc. So I usually recommend filing the I-90 even if you are also filing the N-400 (though it's not required).

The temporary stamp you are referring to is based on having filed the I-90 rather than the N-400. If you file an I-90 and the new card is not issued prior to the expiration of your current green card, you can call the USCIS National Customer Service Center and schedule an INFOPASS appointment, where they will stamp your passport to show you are a permanent resident with a pending I-90. The stamp is valid for work, travel, etc.

The IR7 marked on your card is only relevant if you think you may have automatically derived US citizenship from your father under the Child Citizenship Act. This law states that "A child born outside of the United States automatically becomes a citizen of the United States when all of the following conditions have been fulfilled:

-At least one of the child’s parents is a U.S. citizen by birth or naturalization;

-The child is under 18 years of age;

-The child is residing in or has resided in the United States in the legal and physical custody of the U.S. citizen parent pursuant to a lawful admission for permanent residence."

If all of those things happened while you were under 18, then you actually would not need to file an N-400, but an N-600 and a US passport application. Otherwise, N-400 is the way to go.