Is GST Mandatory for Affiliate Marketing within India

Dear Sir

I am interested to start Online Affiliate Marketing ( Digital Marketing ). 

I have following queries regarding GST :

1. Is GST registration mandatory for Online Affiliate Marketing (Digital Marketing) within India (if Sales Below 20Lakh ) ?

2. Is GST registration mandatory for selling digital products (ebooks,pdf,web templates) within India from OWN Website (if Sales Below 20Lakh ) ?

3. Is GST registration mandatory for selling digital products (ebooks,pdf,web templates) within India from ecommarce Website like esty,amazon,flipkart (if Sales Below 20Lakh )?

4. Is there any exemption for GST registration for providing Inter-state ( Within India ) Affiliate Marketing if sales does not exceed Rs.20 lakhs.

Kindly advise. 

Regards,
Rohit