You are the best informed newbie and you are not misinformed. You have asked very well thought out and researched questions.
It is best to file for your daughter now while you are an LPR. File as soon as you can. File it today.
If you take your oath of citizenship before her 21st birthday, CSPA automatically freezes her age on that day. Later on, you can submit a photocopy of your US passport or Certificate of Citizenship to upgrade the case to the Immediate Relative category. If you take your oath on October 31, your daughter's CSPA age automatically freezes as under 21.
If you wait to file as a USC, you will waste 2-3 months waiting for your US passport or Certificate of Naturalization in order to file. Time your daughter cannot afford to waste. If you take your oath on October 31, then it will take at least one day to get a US passport or the Certificate of Naturalization. You file on November 1 and it is too late for your daughter's CSPA age to be under 21.
I disagree with Aleful. I believe there is a great benefit to file now while you are an LPR since you can freeze your daughter's age automatically on the day you take your oath of citizenship.
--------VERY IMPORTANT-------------------------------------
Write a letter requesting your citizenship be expedited because of your daughter's pending I-130. YOU NEED TO FREEZE YOUR CHILD'S AGE. Try to find the contact information on your interview letter and call them and ask whom you should send the request to.
Bring a copy of the letter to your interview. Tell the interviewer to expedite and arrange for your oath before Nov. 1.
Your child aging out is a VERY GOOD reason to expedite your citizenship.
Good luck.
I don't know much about this except from what I read here. The way I understand it, it is best to file for your daughter while you are a permanenet resident, and then upgrade the petition once you become a citizen. Look here:
http://www.visajourney.com/forums/topic/110679-child-aging-out-cspa-may-help/
