Should always check with your TFS first but PL is always your first point of contact for any assistance required that you have no idea who to approach.

There's a reason why PL are assigned to you and there's also a reason why they're a PL. They have a responsibility to fulfill when their took up that role. They have the connections, and should also have the knowledge. If they don't have the knowledge, they should have the connections/ability to help you seek up the knowledge you need.

Yup, if you have no project, you're considered benched. Generally when you're benched you will be helping out BD bah.