Bcd

yes BCD will remain even after GST comes in force. 

BCD is basically duty to prevent other counties to dump cheap goods in india and it is sort of mechanism to safeguard indian companies and keep a level playing field for indian manufacturers.

there is no credit for BCD and it is always calculated in cost for purchase and it cannot be claimed. it is basic raw material or input cost.

if goods imported for reexport you get DEPB special import licence where BCD is exempted against gaurantee of re export.

i hope the above answers your all questions