You got it because eBay gave it to you. Note that the insertions come off your 40. They don't seem to be additional.
As far as the unlimited freebies, only eBay knows. The last one was November. Maybe eBay has decided not to offer them anymore.
I assume it's a different account. Stores generally don't get them. Why do you need extras? You get at least 600 listings with a store and you have 16 items listed.
