Does this game have any sort of free skate mode?

Jet Technique is the closest thing to a free skate mode, I wouldn't include Jet Graffiti since there is an objective - spraying all of the mandatory tags.

In Jet Technique there is a time limit, but there is nothing mandatory to do nor enemies to avoid. When you allow the time to expire you get to keep any Graffiti Souls collected regardless of how many points were accumulated. AFAIK you get 600 sec. and the only tags are optional small ones scatttered about. It's a nice amount of time to roam, try out various grinds, and see how a stage interconnects with little/no pressure.

Jet Technique isn't unlocked for areas until near the end of your first playthrough. Hope that answers your question!