Olof Simren - Microsoft Dynamics NAV & 365 Business Central Blog

Yes, there is a function on the posted sales shipment that allows you to undo a shipment. It assumes that the shipment has not been invoiced and that no item charges have been applied.

Yes, a Customer can be deleted if there are no transactions on it within the current fiscal year and no open transactions (transactions = customer ledger entries or service ledger entries). There should also not be any sales documents (orders, quotes, invoices, etc.), jobs or service items for the customer. If deleted, the transactions will get a blank customer number. Think twice before deleting a customer with transactions.

Yes, Dynamics NAV allows you to create sales quotes without first creating a customer. You need a contact though, and once the quote is converted to an order NAV can create a customer record based on the contact.

The bill-to customer determines the prices and discounts that applies, it also determines the dimensions and posting groups.