Form AR-11 (US address change)

Does anyone know the answers to the following question?

I hold a H1-B visa and recently plan to visit home in China. I just realized that I have never registered with the US governement (they require to submit an AR-11 form each time aliens change the address). So my questions are:

1. Do I need to submit this form before I go home?

2. In the form, it asks for "copy number from alien card". What alien card is that? My H1-B card?

3. Should I say I am a "temporary worker" in the U.S vs. other categories such as visitor, permanent resident and student?

4. Date of entry into U.S. -- should it be my last date of entry, or first entry date?

5. Port of entry into U.S. -- does it mean my first flight stop in my last trip returning to the US? Or something else?

Truly appreciate any kind of feedback!!!