Can i claim american citizenship through my mother , grandfather or great grandfather ?

Possibly. You should obtain all birth certificates and records to proof that they were residing in the US.

More information is needed to determine if there are options for reapplying. Consult with an attorney for guidance.

Can i get green card after marrying U.S. citizen after august 9.2018. if i overstayed on a J-1 visa for 2 years?

No you can apply for adjustment of status through a good faith marriage to a USC despite the visa overstay.

Can i travel to San Diego ?

Yes travel domestically by car should not be an issue but bring your identification and DACA approval notice.

After separated legally

If you are legally separated and getting a divorce provide this information at interview.

Can undocumented person fly back to his/her home country ? Would be any problem at airport?

No she can depart without issue but if she ever wants to reenter the US she would be dealing with bars to admissibility.

What’s the documents I need from my brother when I petition him and family ?

Form I130, both of your birth certificates and your naturalization certificate or passport.

Do they approved my visa

Based on these facts it is not clear whether your case has been approved or not. Remain patient and wait until a decision has been made.

Do I need to resend form i-765 using the most recent form? Would they reject/deny my application?

Yes you can either resubmit or wait for the rejection notice due to expired form.

Brother’s student visa application and naturalization

No your brothers student visa should not impact your naturalization petition. Consult with an attorney for guidance.