First of all watching August unleash hell on Magnolia and the guild, thanks Mest you did a great job protecting the guild. Dam idiot jerk.
So Cana actually went through with it, and Fairy Heart is unleashed, which I think is probably going to be a key to stopping this Universe One spell, depending on what the spell does.
Irene and Zeref is very confusing, though out the chapter it seemed Irene doesn't full trust Zeref, than the next moment she seemed fully loyal to his war, people from Ishgar like Irene and Zeref they should be warry of Zeref, since they knew who he was all long, un like the natives of Alverez who didn't know about the Black Wizard and just saw him as the for ever young Emperor.
Does Acnologia take Irene seriously, he seemed to with his words, but he never turned into a dragon, if he truly thinks of Irene as a worthy foe, he would unleash his full power. So if Irene does at least temporary take down Acnologia, we have the loop hole that Acnologia arrogance did him in.
So next chapter Fairy Tail Zero, what does that mean, well the countdown never end. Maybe Cana will turn into Zera for a moment, if you go by my reincarnation theory maybe.