Gst for export-only income (from services) exceeding 20 lakhs

Hi, 

I am a software freelancer working exclusively with foreign clients (aka, export of services). In FY18-19, I had income exceeding Rs. 20 lakhs. As mentioned, the income is solely from export of services.

1) Am I liable to register for GST?
2) Do I need to make regular filings?
3) Is all my income (export of services) zero-rated?

Thank for taking the time to answer my queries.