Does anyone know when the street section of competition was added to Unicon, or has it been included since the start?
The first official Street comp at Unicon was held at Unicon XIII in Langenthal, Switzerland, 2006. The first formal Street competition I’m aware of was held on September 19, 2004 at the California Mountain Unicycle Weekend. In Lloyd Johnson’s driveway, in Truckee. Appropriately, Dan Heaton was the clear winner. 
There was talk of an earlier Street comp of some sort being held in Connecticut, but I don’t have any information about that one (would love to learn more). So you see, Street as a competition event is pretty young. The first Unicon was held 20 years before that MUni Weekend.
What were the original events at unicon? I assume freestyle was one.
Freesstyle and Track were the main ones. No outdoor racing (it was on a 200m indoor track; in fact all competitions were in one big room. Standard Skill didn’t exist yet. We did have a basketball tournament, or at least a game. No Hockey.
Off the top of my head, here’s when some events were added, or first used at Unicon:
Unicon II had an Ultimate Wheel Endurance contest. Host Ken Fuchs rode continuously for about 17 minutes.
Unicon III had a “Compulsory” event, that was combined with the Freestyle or “Pre-Standard Skill” event to determine the world champion of each.
For Unicon IV, the event wen from a weekend-based, 3-day event to a full six days. Standard Skill was introduced. Also we had a full round-robin basketball tournament, off-road race (which we called UMX at the time), Coasting competition, Downhill Gliding time trial, and an 8k Road Race (on Track unicycles).
Unicon has come a long way.