I can't speak for the first question, as I've only bought individual tickets in the past.
Last year the 4 day pass tickets sold out in 30 days from what I remember reading, and the daily passes sold out a couple of months after that (though Friday and Saturday sold out much earlier than the other days). However, given that 4 day + preview night passes sold out at Comic-Con this year, there may be more of a rush for passes this time around. Though I doubt they'll sell out within the hour, I'm personally planning on getting my pass ASAP just so I don't have to worry about it.
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Last year the 4 day pass tickets sold out in 30 days from what I remember reading, and the daily passes sold out a couple of months after that (though Friday and Saturday sold out much earlier than the other days). However, given that 4 day + preview night passes sold out at Comic-Con this year, there may be more of a rush for passes this time around. Though I doubt they'll sell out within the hour, I'm personally planning on getting my pass ASAP just so I don't have to worry about it.