Thanks man,
So in short you really dont need to send any AC21 Letter at all.
----------- if you send it does not hurt
Just need the offer letter from the company that you are working at the time of the 485 interview.
------------ not every I-485 gets INTERVIEW,95% of I-485 are approved without interview. if you update USCIS before I-485 approval with AC21 request that is good
The 485 interview is really 8-9 years in future. So why bother sending AC21 letter every time you change the company.
----------------that is up to you to send or not send. read the latest AC21 Memo
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