Pl refer two important circulars issued by Govt on 1.7.2017 and 4.7.2017 for export under bond:
https://www.cbec.gov.in/resources//htdocs-cbec/customs/cs-circulars/cs-circulars-2017/circ26-2017cs.pdf
https://www.cbec.gov.in/resources//htdocs-cbec/gst/circularno-2-gst.pdf