回复：question 1, 2 and 4

For your questions:
1. The city of airport where you passed border check and enter USA, of course it is LA, from LA to New heaven no more the international airline.
2. Not everybody has it, I believe you have no this number yet. Just fill N/A.
3. I do not know this.
4. I believe it is normal envelope, 9.5 x 4 inch. Of course it is not the envelope when you send the payment check.