Did you marry? A K-1 fiance cannot file an I-485, but a spouse can. A fiance can file an I-765, but it would not get approval before the expiration of the I-94 (90 days after entry)., thus making it useless.
1. That depends on whether the new immigrant wants to work legally.
2. No, not too late. You can submit an I-765 after filing an I-485. Cost is $260.00
3. 5 years, I believe.
4. It Doesn't matter. Make sure you include the receipt for the I-485.