Xiaobaitu and other experts, help!!! on I-485&131 form

I have some questions:

1. On I-131, Part 1 Q#3: Class of Admission? I came in US as F1 and now H1, what should I use here?

2. Since I apply for AP, I can skip Part 3 Q#4 untill Part 7, right?

3. On I-485, should I use "none" or "N/A" for middle name and Address-C/O?

4. On I-485 Part 3B, List your present hu*****and/wife, all your sons and daughters. My kids were born in U.S, do they have an A#? If they do, where should I find the A#?

Same part, there are only two letter space under "Middle Initial", should I leave it blank or "NA"?

5. On G-325A, "Applicant's employment last five years", I worked several month as an intern when I was a student, should I list it here?

6. Also on G-325A, the last column of first line, "File Number", what is that?

Any help is appreciated! Waiting on line!