Hello,
1. No, you were not required to take TCS registration under GST since you would be selling your own products on your websites. You must apply for cancellation. Till cancellation is processed, keep filing Nil returns under this TCS registration to avoid any late fee penalty.
2. GSTR-1 -monthly/quarterly, you can opt for it and GSTR-3B monthly. If you would be selling your products out of India and receiving Foreign currency for it, it would be termed as export of goods. Under exports, you will have two options, either supply after paying tax and later claiming a refund of the unutilized ITC or apply for LUT and supply without payment of tax. Other than that, GST annual return plus Income Tax compliances.
3. Tax rate on E-book is 5% - HSN 9984. The tax rate on unprocessed green tax leaves is Nil other than that, it is 5% for all other Tea varieties under HSN 0902.
4. Yes, you can use the same GSTIN registration or both businesses. Better if you separate the records for reconciliation purpose.
I hope this answer satisfies your requirement.
Regards,
CA Hunny Badlani