immigration process help

[diptibshah]

hello

I have few questions about immigration...

1. I am US citizen and now i would like to invite (file) immigration for my mother so within how long she can come to US

2 After my mother comes to US, she willl receive green card, how soon she can file for my brother (21+)

3. If she can file for my brother can she does that even if my brother is in US on Student visa

4. If my mother can file for my brother how long will it take my brother to get his number

5. Does my brother needs to stay in US after his study or he can go back

6. Will it better that my mother file for my brother as soon she gets green card or after she become US citizen.

thanks