In my experience, both are needed. Product owners and developers who understand the product. It's possible to have both, they're not mutually exclusive.
Yes, but it's the Product Owner's responsibility to clearly understand the requirements from both customers and the business and communicate them clearly to engineering.
Having engineers handle "support calls" doesn't make much sense, they are not equipped to manage product feedback or understand the business implications.
Having engineers handle "support calls" doesn't make much sense, they are not equipped to manage product feedback or understand the business implications.