Urgent question about U.S.Citizenship

I have an urgent question about citizenship. I got my green card about four years ago and stayed in the country almost all the time except four weeks out of country for vacation. I now got a job in China and want go back. I noticed that immigration website mention something about three month before filing, I have to physically stay in the state that I file the application. I just consulted several layers and some said it is not a requirement. Does anyone could share this information with me? BTW, I got my GC October 03, if I file application July, three months means April to July or July or October.

Thank you so much for your help.