For 2 1/2 hours I heard snapping, cracking noises (like breaking a twig) in the ceiling of my living room making the tiles on my floor come up. In two rows in a straight line, through two rooms the tiles went up against each other way off the floor like a pyramid shape.. Eventually most of the tiles in the room came loose from the floor and the grout crumbled. Over a couple of years I heard it for 5 to 15 minutes through out most of the condo ceiling, and two walls, and the rooms also had the tiles come up, sometimes with a bang like a gun went off. The latest guess is it is the cement floor above me. The building has 8 units with 4 on each floor and is about 35 years old in Florida. The floor above did have water problems and water entered from a hurricane. Newly installed windows prior to the 1st ceiling noise now have a popping noise when the weather changes during the day or night, especially in the late evening.

Is the 2nd floor rebar and cement going to fall apart? What could have caused this noise all through my condo?

It's impossible to know without seeing what is going on upstairs, and also how the building is constructed, where water pipes run, and what the storm damage was. This is a question for the building management or co-op board, to determine how much of the entire structure is affected.
I wouldn't imagine that the floor above you is going to collapse, but certainly an engineer needs to inspect the whole building. I would demand it, even if you have to hire someone and then sue for the cost.
Windows popping is indeed related to temperature changes and materials contract when cold and expand when warm.

To be proactive, go to the town for a copy of the building plans, mainly to see where water pipes run, and to show to a contractor or two for estimates on repairs. Try to get your neighbors to let you in to see what state their units are in, and to solve this together if need be. But don't forget to hire an engineer to and to make it clear that the association pays for it (if it isn't just your upstairs neighbor's fault, which doesn't sound like it). You might ask the building inspector to look at the place first.