Old Xbox 1 games on Xbox 360

[jgdc74]

I'm a bit of an Xbox noob, and never owned the original console. Mainly because I was sick of all the console manufacturers giving us crappy PAL slowdown and borders (I live in the UK), and I always bought import stuff from the US and Japan, and the original Xbox just never interested me.

I have a couple of questions:

1) I now have an Xbox 360 and I like it, and am glad to see the the old PAL and NTSC issues with consoles past are gone. I am just getting into all things Halo now.
I want to get Halo 1, and can see that it is available from the Xbox live store. Now, as I'm in the UK, will I get a PAL version of Halo or an NTSC version, or would it be the same the world over? I do not want one with shitty PAL slowdown and borders!

2) I have heard that Xbox 1 games will work on a 360. Would a US NTSC copy of Halo 1 work on a UK 360? Maybe that's a dumb question, I don't know, people are saying different things.

Thanks in advance for your replies.