Dumb question, but how did he start playing Dota 2 at the age of 7? Surely thats a mis-print - it's not been out that long? Development only started in 2009...
Dota was originally a custom map for the Blizzard game Warcraft III released circa 2005. In 2011 Valve hired the developer of the custom map to make a full standalone game and that became Dota 2. Most players (including me) played the original game before shifting to Dota 2.
They probably meant Dota 1. Dota 2 is an HD remake of Dota1 with the exact same units and game mechanics so most players consider both games to be the same thing.