We were able to upgrade to annual passes with our "buy 3 get 4" tickets. I chose those because the value of the free 4th day was a little better than the value of the free 5th day. If you use the tickets before upgrading, you will get the full gate value of whatever length ticket you have.
Yes.
But, be sure to actually USE the tickets to go into a park at least one time BEFORE doing the upgrade.
After you use the tickets for entry, you will be able to add up to 5 additional days to each ticket (total of 10 days per ticket) for just $10.65 per day added.