Question 1: Most likely, you will have to recreate your account if it was created after that date. I'm not 100% sure, but most likely you will.
Question 2: I imagine it will run for about 2-3 weeks. I believe that is a little more time given than in December, but we will also have double happiness, double exp., etc give once the game is back up.
Question 3: Any progress you made after that date is lost. If you donated money for a Mewtwo (Armor) you will get them back, if you traded, that's another story and you'll have to retrade.
Question 4: Patrick has stated he's set up an ICloud and I believe 2-3 other spots that will all do a backup every 24 hours so if something should fail, it can all be retrieved and at most 24 hours will only have been lost, instead of what happened here.
I know I'm not part of the mod team, but I thought I've give you the best answers I know of.