(at around 31 mins) The guards are firing at Black Canary and Speedy and hitting the sofa, which sparks with each bullet hit. They then use the overturned sofa as a shield against the bullets before resuming their assault. The sofa would never spark and would never stop a bullet unless one by a very slim chance hit a metal bracket inside the sofa.
The code to open the Kord Industries loading dock is 4587, Oliver punches in what looks like 6521. However, Green Arrow is hanging upside-down, and the scene was most likely shot with him right-side up and then flipped (probably so his arrows wouldn't fall out of his quiver). So, punching in 4587 in a keypad, which is then flipped upside-down ends up looking like 6521.