SGST gst on export of services

We have provide services to party situated in Singapore. services includes web hosting and maintenance for video content. we have raised invoice in INR without Charging any taxes. how do we deal this case for get payments and returns.

1. Tax is payable or not?
2. If yes, refund /ITC will be available or not?
3. Can we go with Bank Guaranty if don't want to pay tax?

need urgent help and advice