Previous visa info

I want to apply for a L. I have been to China as a tourist before. Details regarding these previous visits are requested, but I don't have this info as it was in my previous passport which no longer have (I needed to renew it). How should I go about this? Remain silent, or stating that I have been there but don't have the details?

Also, although this has been asked before, just to be sure: the application is not entirely clear as to the necessity of having an 'inviter' when you enter on an L (section 2.8) - it is my understanding that a a return ticket + hotel bookings suffice (and they did in the past), but is this still the case, and if so, do I leave 2.8 blank?