[Sabio]

1- I have a problem that my surname name in passport, doesn't match that in medical diploma ,it is the same name but in passport they put the name of the family or tribe ,but in diploma the name of grandfather ,does this would make me any problem in registration?

Yes, you will definitely face a big problem. The ECFMG will not accept your application even if there's a single letter difference between your diploma and the ID that you'll use in registration (in your case the passport).
You have one of two options; either contact the college and ask them to change your last name in the diploma and the transcript. Or try to produce another passport with first name, middle initial, and last name all matching your medical degrees papers, all of your documents should match the name exactly.

2- I would like know ,exactly ,what they need from college in verification?

Please read this thread
http://www.usmle-forums.com/recommended-general-topics-threads/362-ecfmg-registration-steps.html
They need to fill special medical credentials verification forms, send your transcript, and approve your diploma, and sign your Form 186.

4- When should I contact the Prometric company to arrange the exact date of the exam?

Only after you get your scheduling permit. For more details please read here
http://www.usmle-forums.com/usmle-articles/719-usmle-prometric-practice-test.html
Also search the forums for Prometric and you'll see many useful threads.

5- I need to know ,in my case which should be better to start is step 1 or step 2 & how long it would take each in preparation?

Please see this thread/poll
http://www.usmle-forums.com/recommended-general-topics-threads/1223-step-take-first.html