Assuming you have the cap on and tightened appropriately, it will hold the water just fine. However if it's upside down and in a bag, there's a decent chance that something will push on the cap's clip/lever with just enough force to open it. Remember, they're meant to open with the force of your thumb, so that's all it needs for something to dump the liquid inside.
The number 7 in a triangle has to do with recycling. Nalgene no longer uses BPA in their water bottles - it says BPA FREE next to the 7. They have not been recalled, but responding to consumer pressure the company changed the plastic they used for their bottles in 2008-2009. Mine has no odor.
Two things I have finally figured out about this bottle. 1. The spout does open. You have to kind of twist it a little and it finally comes open. No, you can't fit your hand inside. I just put mine in the dishwasher. It is a nice bottle. I enjoy using it.