What are key factors to consider choosing full-stack development company?

I have few questions to ask:

1. What are the biggest challenges facing full-stack development companies today?
2. What emerging technologies are most exciting for the future of full-stack development?
3. How can businesses ensure they are getting the most value from their investment in a full-stack development company?
4. Share your experiences (positive or negative) with working with a full-stack development company?

Can anyone answer this question?