Point 1 - I read that setting up a controlled demolition itself would require so much preparation that there's no real way they could cover that up.  As for separate explosives?  I couldn't say, but also I'm not sure if they'd have a significant effect.

Point 2 - I read those little tufts of smoke below the collapse of the buildings were pockets of air being expelled from the buildings, most likely from the elevator shafts.  That makes sense to me...

It is possible there were explosives somewhere, but probably not, and I don't think it could have been a controlled demolition.