gstr 3b

No GSTR-3B can't be revised. What ever the changes that needs to be considered in GSTR-1, 2. Part-B of GSTR-3 is for the reconcilation of differences between the GSTR-3B and GSTR-1 & 2.

MODIFICATION  WILL NOT BE ALLOWED AFTER SUBMIT THE RETURN , WHERE AS THE CHANGES CAN BE DONE IN NEXT MONTH RETURN 

No problem, whatever your suppliers mentioned in their GSTR-1, it will reflect in your GSTR-2A. you can make changes to it in GSTR-2. you just accept those transactions which you forgot to claim in GSTR-3B