Okay so everyone is kind of confused about D5. The synopsis says When Wonderland plays host to the Kingdom Cup Games, Red and Chloe must fight to save everyone from an unexpected villain.
People are also disappointed that D5 won't have the Young Villians and that Uma's warning about messing with time has no effect. I currently believe that in D5 Chloe and Red will believe everything is fine and that they managed to get back without changing too much besides some small surprised (like Pink) however near the end when they face this unexpected villain they will realise they messed things up more than they realised and D5 will end with them planning or actively going back in time.
In D6 Red and Chloe will face a serious of choices trying to keep things as close to the original timeline as possible while still saving Cinderella's life. Red will have to deal with the fact that she will possibly be erasing the sister she has gotten to know and care about. In D6 we will discover more about the prank and we will get to see castle coming.