if i file a prior year return even though i have to mail it, does it get accepted immediately

Yes they take all mailed returns.  Only efiled returns gets Accepted or Rejected.

I believe you are asking if the return will be accepted and processed immediately, as happens with a current year return you e-file. If so, typically no, the prior year return will not be processed as expeditiously as the one you e-file for the current year. 

Mailed returns are not "accepted" or "rejected" in the way that e-filed returns are treated.  The IRS will open your envelope and enter your mailed return into the system.  It usually takes three to four weeks after mailing the return for that to happen.  Then you can watch the IRS refund site for information.

You need your filing status, your Social Security number and the exact amount  (line 35a of your 2024 Form 1040) of your federal refund to track your Federal refund:   

https://www.irs.gov/refunds