MacBook bought as new could potentially be a refurbished older model
Click on Apple Menu -> About this Mac...
It should tell you exactly which hardware version you're using -- e.g. mine says "MacBook Pro (Retina, 15-inch, Mid 2015)"

If you want even more detail, there's a free app called MacTracker https://itunes.apple.com/us/app/mactracker/id430255202?mt=12 on the App Store that will provide even more info.

As to the second and third questions...shrug