In order to get funding, you need much more than a revenue stream. You need to show the investors that you have carefully built your business to withstand any challenges that face you. Sales is important, but if you are surrounded with the wrong people then you won't go anywhere.
If you ask me #6 is the only one you need
#6 builds on #5, so you need that too. #5 would be a good first milestone, so that is #2. A list of your milestones would be a good foundation for your business plan (#1).