回复：A little confused, sorry to bother again

Can I use my vacation for this short leave or I have to use unpaid leave?
- It's wouldn't be easy for USCIS to differentiate them, and neither would USCIS do
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Then how can USCIS tell whether I am working or not?
- They do NOT know it.

There must be some procedure for them to determine my working status, for example, they can check my W2 form.
- W-2 tells nothing but your paystubs may

BTW, for the sake of my 485, do I have to maintain my position in my current company?
- At least 180 days if you're not NIW

Do they need to keep a postion for me to validate my 485 application?
- At the time of interview

For example, my employer terminate my position now, can I come back to work directly when I get H1b extension or EAD card.
- H-1 has to be sponsored by this employer

It is very scaring if I may lose my 485 application.