You need no longer get registered below GST regulation. In case you your annual income is greater than 10L and staying in positive prescribed states then you have to get GST registration. The purpose on your customer’s insistence on your registration is they cannot claim input tax credit score above that they've to pay & claim the GST under Reverse Tax Mechanism since you are not registered. So it is better to get voluntary registration although you are not accountable for registration https://123gst.com/gst-registration/registering-in-gst

I think we need an absorbing surface and tile cannot, hence it must be sticky

Unusual

When it is dry i.e. after 48 hrs apply a coat of varnish over it, it will protect it

You can use Modge Podge for photo transfer

Decoupage is gluing paper on surface, you can use colours on paper.

no...for glass you can buy glass painting colours

Ya

Yes you can. I have made a lot of decoupage bottles and used fevicryl acrylic colours.

Yes

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