My understanding is that they actually haven't tested at anything but -80C, and that it is potentially possible that it could be stored at higher temperatures, but it hasn't been examined yet.
Dry ice is very common, and you get 5 days at refrigerator temperature. Everywhere in the world is reachable in 5 days if you need to. It gets really expensive to charter flights to many areas, but it is possible if you have money to burn.
Of course we now have reason to believe that vaccines that don't need dry ice will be approved, so logistics will direct the easier to ship ones to remote places.
You can reach everywhere in 5 days but that's not enough. People have to come and get it, there's also a chance there will be a slow start due to concerns over a new drug that the media may emphasize was "rushed". Then there's the logistics of scheduling so many people. If you don't bring yourself a cold storage freezer you're committing to using 100% of your doses within 5 days which may not be possible.
For the first few months all doses will go to high risk people. Most won't have the option to refuse it.
Eventually you are right. If the Pfizer vaccine is to be used in remote places the people getting the vaccine will need to schedule it in advance (and probably pay for it) to ensure that once it arrives it is used.
It is, especially for far flung places. This stable vaccine will be very useful in places like the pacific islands, where air transport isn’t always an option.
Any island that doesn't have air transport doesn't really need the vaccine (if transit take weeks, infections on ships burn out before they get there).
Realistically, every major population can be reached in 24 hours by modern transport, and the Pfizer 5000-dose transport package keeps the temperature for 5 days.