1 - Not very long, should only take about 3 minutes or so. Class IV creek.
2 - I think it's just "run what ya brung" all in one category.
3 - Plastic would be the call, it's bony.
4 - Not sure, maybe 20 or so.
I've not raced it, or even run it this season, but it's a fun run and even though the race is over at Steamboat Blvd bridge, you'll want to run the rest if you've never done it.