GC applied, I-485 pending, can we leave US without AP & enter US back on existing B1/B2 visa ?

most likely they will be stuck outside of the US. you will have to transfer the case for adjustment through consular processing, which will be a...

Hi I completed my interview and applied for work permit but I haven’t got it ?

There is no such thing as an interview for a work permit. most likely you had an interview on an application that also gives you a right for a work...

Will my joining the Army Reserve put my mother, who is undocumented, at risk of deportation?

No. Actually, it can get her a green card. You should consult with an immigration attorney.

You can live anywhere in the US and apply from wherever you are.

What steps do I need to take if my brother was deported and bared 10yrs in March 2009 from the United States for possession.

He has to talk to a lawyer to figure this out. He can have a phone consultation from wherever he is now.

Apply for the political asylum

You will have to have a very good reason for why you have not filed within 1 year of entering the US. You should consult with an immigration lawyer...

I filed for asylum but check the convention against torture box. i only realized that error after about 2 years.what can be done

You can fix it at the interview with an officer.

Green Card for mother??

He still can do it but he should do it ASAP.

Should I file jointly or separate?

You should consult with a CPA about tax issues. The immigration service will want to make sure that taxes were done correctly.

I want to my wife to come with me to the US.

You should be careful about maintaing your presence in the US for naturalization purposes. You may get yourself not eligible by your absences.