This is separately developed version of Minecraft that has no relation with the mobile nor PC version.
About Minecraft: Xbox 360 Edition
According to Wikipedia, this version was created from an old PC version, but now, with several updates, is close to the current PC version. If it is true, I think we can consider it port of PC version.
Possibly so. I only confirmed that they're not developed in tandem nor is there aim to make them compatible in multiplayer or even to have exactly same content/mechanics.