Regarding the difference between ça and cela, the lesson states that "Ça is the shortened form of cela. Cela is quite formal, so you'll hear ça used much more frequently."
As for ce, it's also a shortened occurence of cela, but will only be used in front of a verb, neither on its own nor at the end of a sentence:
Ce sera bien (It will be good)
I hope that's helpful!
À bientôt !