Hi, if you bought X-plane from Laminar research, you just need to download the installer from there and follow the steps :
http://www.x-plane.com/kb/digital-download-install/
If you want to install beta versions, you need to specify it. I have noticed strange behaviours too, For example the default cessna 172 struggles to intercept the localizer. She seems to take the selected heading into account and never deviates more than 30 degrees from it. I haven't filed any bug report so far, though.
The last version is currently 11.02b1a