Phew, so many questions... Don't honestly know. I've not actually used it yet. I'll have a look later, but i think yes it would need to secure there, or at least to somewhere else as its only secured at the front then if not. It's another minor question for me though as looking at my own pics it will need to secure onto the pillion pegs, which are not present on my bike. But they're not exactly a 2 hour job, only a 5 minute job.
I only bought the bag for a specific trip, which isn't until the end of June, so after fitting it for testing, i then put it in the box again.