The flashback with Laurel from "Eleven Fifty-Nine" is different from what actually happened. Laurel's line "...tonight it was just a reminder that anything can happen, which is why I need you to promise me something" has become "After tonight, I realized anything can happen. Which is why I need you to make me a promise".
Malone refers to Tobias Church's practice of putting coins on the eyes of his victims as his MO. MO is modus operandi, and it refers to the practical aspects of the crime; how the criminal carries it out. The coins are what would be called Church's signature.
Laurel's hospital bed has none of the side rails up. The upper side rails are always up unless staff is present at the bedside to prevent patients from falling from the bed.
When Green Arrow uses his bow to shoot an arrow up to the next level in the power plant, there is an explosion and he appears to lose his bow, The next scene he releases the cable and he is holding onto this bow.
At 39:25, the map behind John shows the countries of Croatia and Serbia, however, you can clearly see that the city of Belgrade is in Croatia and the city of Split is in Serbia. Belgrade is actually the capital of Serbia, while Split is a city in Croatia, so the map behind John is incorrect.