2 Points
Joined September 2017
CGST Payment amount in other than reverse charge should be equal to the outstanding liability. - error is because of GST portal, wait for some time to fix error by them and regarding GSTR1 & 2 yes you can file w/o filling GSTR3B But make sure payment has to be done w/o making any delay , then you have a time upto 10.09.2017 to file GSTR1, GSTR2 also got time extened upto 25.09.2017. Relax for the moment