MBA having random hangup issues

I've had some issues with my 13' 2012 MBA, it sometimes shuts off when I put it on a book (probably something short circuits when light pressure is applied on the base).
When I transport it, it sometimes looses battery connection and when I open it the recovery of session starts (greyed screen with little progress bar).
Yesterday, I was fighting with the WiFi, it wouldn't connect to my iPhone tethering option nor the café's wifi; the wifi bar said it could connect, but no Internet. Then as soon as I would press something in the system preferences in the WiFi section, the whole thing would freeze and I needed to Force Quit system preferences. After 2-3 reboots I finally got around to it working, but the status bar wouldn't correspond to the system preference section.

Now I haven't taken an appointment with Apple yet because the only store in my city is overbooked on Mac Geniuses.

Now I wanted to ask you guys if any of you had similar issues?
Also; if ever I need to replace it, is it possible to upgrade to the rMBP 13" (my original plan but only the 15" were announced) in store?