Yes can claim whose invoice are not shown in Gstr 2a but you have to upload the bills which are not shown in gstr 2A in annexure-B or you can ref the circular no 125/44/2019
No you are not eligible for refund of invoices which are not reflected in gstr-2A, you have to consider as per gstr-2A please go through the circular number 135/05/2020 dated 31-03-2020 and circular 139 dated 10-06-2020.