Immortal Platypus

Yes, Rand and Moridin switched bodies. As for the rest of the stuff, I'm not sure, but I think that the first age will end in a big war and the loss of channeling, and then the second age ends with channeling being rediscovered, which kicks off another age of legends. This is assuming there's only four ages though, which might not be true.

BUT HOW DID THAT HAPPEN? He just drew too much power through him so they switched? And what happens at the end of the 5th to turn it to the 4th? my brain is exploding

The Wheel of Time is a wheel with seven spokes, and each spoke represents an Age. The Third Age is the one that ends in the books, the Second Age is the Age of Legends, and the First Age is… our age. There is, in Tanchico, I believe, a collection of relics from the Age of Legends and the Age before it. In the collection, there is a Mercedes-Benz hood ornament. I don't remember if there's a specific event that ends our age, but it does have to do with channeling. Of the other ages, not much, if anything, is known.

Rand is an incarnation of the Champion of the Light, called sometimes in the fandom the Dragonsoul. Every few ages, the Dragonsoul is reincarnated to fight the DO. The DO's prison is not broken open every age, only when the Wheel calls for it to be broken open. As of the end of the Third Age, his prison is sealed. Again, there's hardly no information about the ages besides the Age of Legends and the Third Age, so there isn't a ton that I can say.

Yes, Rand and Moridin switched bodies. They were able to do this because when their Balefire crossed streams in The Path of Daggers, it connected their souls. The explanation that Sando gave was along the lines of "the soul that wanted to live [Rands] went to the body that wanted to live. The soul that wanted to die didn't go to the effort."