Yes, in 'echo 3 true story', 'echo 3' is likely related to the 'true story'. It could be the name or identifier for the events that make up the true story.
In most comic versions, Echo isn't deaf. However, there might be alternate or special story arcs where this could potentially be a trait, but it's not a common characteristic.
Sure, Echo is portrayed as deaf in the comics. This trait plays a role in shaping her personality and the challenges she faces throughout the comic series.