1a. MIGHT prove to be problematic.
1b. What did "Disney" say that process would be?
1c. Again, MIGHT prove to be problematic.
1d. If they will allow the upgrade, you have until close-of-business ON the same day
that you use the tickets' last asset.
2. You can SAVE the new, unused tickets for future use or to help buy new tickets at the time of your future trip.
3a. You can. (Many convention tickets can be upgraded.) But, there is no monetary "advantage" in upgrading convention tickets, as you would only be
given the amount you originally paid for those tickets in the AP upgrade.
AND, if the convention tickets include any Water Park entries and you USE any of the Water Park entries,
you can only upgrade to an AP that includes Water Park entries.
OTOH, if you buy discounted tickets from an authorized discounter (like
UT, ParkSavers, BoardwalkTickets, etc.) you will get to "keep" whatever discount you got with the original tickets
if you decide to upgrade.