Urgent-please help

EB2 filed 485:
1. What other documents related with employment will INS ask for after submiting 485 ( submited with employment letter)?
2. Will INS check for employment status before approving 458 again?
3. If the company closes down after I submit 485 within 180 days, am I totally screwed up or there could be a chance that INS might not know it?
4. If the company closes down after I submit 485, is there a chance I can use EAD to work or it's totally impossible?
Thanks a lot.