Hi,
1. GST registration can be taken for any type of constitution of business. You may choose what suits you best. You don't need to collect gst for classical drop shipping business. However, it would depend upon peculiar facts of your case
2. It could be address of your residential property as well.
3. No, if china supplier is issuing you the invoice and you are issuing invoice to USA customer.
4. Not required
5. Recommendatory because it does not have any filing hassles. You dont need to do any filing.