Iris shows up where Flash is fighting Captain Cold and Heatwave with an open umbrella. There is no reason for her to be carrying one because it is nighttime and it is not raining.
When Heat Wave is brought into the police station, he's handcuffed with hands in front, which police don't do; however, when the cut changes to a shot of police drawing guns on him, then back to him, he is handcuffed with hands in back.
Near the beginning when Captain Cold freezes the door of the building with all the cars in it, the frost is still spreading when the car crashes through the door, but when Cold exits the car his window is up. He wouldn't be able to freeze the door if his gun was inside the car with the window up.
Flash acts on Wells' plan to have Cold and Heat Wave cross streams to neutralize their weapons. While this makes for good theater, Flash could have much more easily used his speed to simply take their weapons away from them before they could react.
The Rathaways transported their new $25 million painting with no protective coverings at all, much less a crate and padding. Even in a private jet, accidents happen, and the painting could easily be damaged merely by being dropped on the wrong surface.