e-filing 問題--謝謝

有幾個關於I140 E-FILING的初級問題,可能聽起來有些幼稚. 提前謝謝大家的回答.
1. USCIS 網頁(http://149.101.23.2/graphics/formsfee/forms/e-i-140.htm#purpose)提到"This form is filed on behalf of an alien, and not by the alien." 什麽意思?不是說我們自己不能E-FILE,隻能請律師吧?

2. E-FILING 的過程是不是:
a. I140 form and the fee by e-filing;
b. At the end of e-filing, obtain a confirmation receipt number.
c. Mail the cover letter and supporting materials (papers, awards,
etc.) with the receipt number.

3. Filing question2: Are you authorized for Centralized Filing? 這個怎樣判斷?一般情況是NO嗎?

謝謝