Gst paid under wrong GSTN

A person is having two GST registrations(GSTN-1 and 2). Actually Invoices are issued under 1 but filing(gstr1 and 3b) is done under 2 and gst payment also under 2 for 18-19,19-20 and 20-21.
Now the recipient of services has withold all the payment bcz gst no filing by service provider. Bcz billing is under 1 but filing is under 2.
Now Reg. 1 is deactivated as bcz return is not filed for a long time and at the same time we hv deposited all taxes under Reg. 2 mistakenly .
Query-
I.) How to get the money back back that has been deposited under Reg. 2.
II) Can we reactivate the Reg1 and to file for all the prvs years(18-19,19-20 & 20-21).