GSTR-2A vs 2B
Form GSTR-2A: Say, if a supplier declares invoice dated Apr'22 in his Form GSTR-1 of May'22 filed by 20th Jun'22, the said invoice detail will be reflected in Form GSTR-2A of Apr'22 only, since the invoice is dated Apr'22. Hence it is a dynamic form which keeps changing every time a supplier declares his past supplies in any of his Form GSTR-1 by whatever date.
Form GSTR-2B: for Apr'22 will have details of invoices declared by the supplier in his Form GSTR-1 submitted from 12th Apr'22 to 13th May'22.
So as per above example invoice dated Apr'22 which is filed in May'22 return i.e. by 20th Jun'22, the same will reflect in Jun'22 Form GSTR-2B not in Apr'22 GSTR-2B.
1. So, GSTR-2B may consists of previous month invoices also
2. It doesn't only show eligible transactions, it consists of both eligible and ineligible transactions. In Form GSTR-2B under ITC Availability column where ever it is mentioned as "No" straightforward those are ineligible. However ITC ineligibility as per Section 17(5) will not be available. That has to be analyzed specifically.
3. Amendment in Form GSTR-2A and GSTR-2B is not possible. However in case of errors ask supplier to amend the same in his Form GSTR-1, so the same will reflect in Form GSTR-2A and Form GSTR-2B in "Amendment" sheet