I managed to get pas the first one, but I'm still having issues with constraining the lens, I've tried parent and point constraints and neither of the seem to be working.
Not sure why constraints wouldn't work. Make sure you do the selection in the correct order (constrained object needs to be selected last). Might also want to check the hypergraph to see your connections; if you get some weird cycling connections, things may break and not work as expected. So for example, if you get…