Since 2000 I have focused my efforts on helping sales organizations improve their revenue performance. My expertise is built around what is called Operational Excellence which depends heavily on managing a sales opportunity through a defined set of sales stages and individual steps in each stage to a logical conclusion. I have also been the architect of using a 'mapping' metaphor for managing the sales pipeline
2) by sales stage, and
3) by large account called Player Map.
To answer your first questions:
1) I recommend no more than 5 stages. Above that number isn't effective to manage.
2) My philosophy is this. One 'markets' to suspects to generate interest and sells to prospects who have been identified themselves as interested.
3-6) I love the remainder of your questions but in reading your query and meaning no disrespect, my answers would honestly depend on what size the sales force is, what a profile of their typical customer would be and who they are attempting to contact. Said differently there is not a one-size-fits all answer.
I would be glad to send you a financial pipeline document for tracking sales opportunities in defined stages. The sales map is customized for each client.