I have been looking at Xbox 360 for some time, I've never had Xbox but now that it's previous gen it suddenly interests me, but if Xbox One can emulate all 360 games then it's really no point getting 360? I just have to wait when One Slim is launched with better everything including price.

Every game and actually a basic OS are recompiled from PPC to x86 as it seems. MS doesn't really tell all secrets but technically it's no emulation. ^^

If you want full access to the 360 library you need a 360 console. The number of titles that are backward compatible on Xbox One is going to be extremely limited compared to the size of the 360's library, with publishers deciding on a case by case basis which games they will allow to be backwards compatible.

No and no.

MS does not have the source code of the original game (except if they made it). Hence there is no way they can recompile stuff.

It really is secret sauce. Super clever stuff.

If a company says no, their X360 cannot run on the Xone. The emulator still needs the assets of the original game and that is copyrighted intellectual property. Equally Kinect games won't wok (although I imagine that part could be sort-of emulated with Kinect2).

My guess is nowadays an X360 is so cheap to buy that it is actually the safer way to go. Unless the emulated games perform better than the original, which I have no idea.

Which might be one reason why they have to request every game by the publishers.

No it isn't. It mostly is/was a massive amount of "grunt work", but there is nothing ingenious about the emulation.

They can recompile the original PPC machine code to corresponding X86 machine code. If this is what they are doing (likely) then it would explain why a few titles suffer from slowdown since translating code in this way often results in suboptimal code for the target architecture.

All I can say is look at the BC list and see if the games you want to play are compatible. Lots of key titles aren't but there's plenty to play and more on the way.