The tutorial and the Future area are free to play -- attempting to go to the Past area will show you the last ingame pitch to get you to pay for Unlimited (at one point called Premium) Access. This represents the first few hours of game content although some folks might have fun hanging around the Future area longer.

Level is capped at 4 and the first 4 nanos are available.

This is first-hand (based on me trying it yesterday). Before release different sources reported different things. Hope this helps.

 As far as trial content goes, that's pretty decent.  It easily took me a few hours to reach level four and get four nanos.  That being said, I'm pretty sure I haven't done all the quests for Future Zone, nor have I explored it entirely.  That's a couple more hours, probably, but will I simply not gain experience or will I not be able to complete those quests? It would be nice if one could explore all content the zone has to offer, regardless of level.

~Ripper

Yes  since I cannot go though the Time machine  I think I just explore  and see if my fascination continues enough to go buy a card.