Should I use file W4 form as NRA or RA under this situation?

Background:

1. I'm on OPT with F1 Visa and stay in U.S. for more than 5 years (2012-2015, 2017-Present).

2. I have proof makes me still be the non-resident alien under the "The Closer Connection Exception to the Substantial Presence Test for Foreign Students" rule of the IRS.

https://www.irs.gov/individuals/international-taxpayers/the-closer-connection-exception-to-the-substantial-presence-test-for-foreign-students

3. I plan to apply H1B (work visa) this year.

Currently, I need to fill W4 form for 2020.

Because the exception rule is only valid for students, I may not be eligible for it if I get my H1B.

My questions are:

If I fill the W4 form as NRA now, and I'm no longer the student in October, what should I do in the tax season of 2021?

If I fill the W4 form as RA now, can I get my money, FICA, back for the specific period (present-September) in the tax season of 2021? If yes, how to get it?

Thanks!