Few Questions about PSN's connectivity limitations...

Hi guys! I had this question about the PlayStation Network which I thought I shud ask.... The PS3s locally available here in my country are Japanese....Now I know that PS3 games are region independent, but what about the PlayStation Network ??

For example, if I try to open up the PlayStation Store on my Japanese PS3, from here in Pakistan, can I open the US or European PlayStation Store websites, or just the Japanese one...?? This thing is that I am bit worried about the 'Japanese' part....the content available there (game demos, movie trailers, etc..) might be Japanese, for Japanese people, which could pose a problem...

Secondly, what about game content ?? Will additional game content be dependent on the region of the game, or the region of the PS3 ?? For example, if I have a Japanese PS3, but a US copy of MGS4 (when it comes out inshallah), will I be able to download the US content available for the game, or the Japanese content........or none at all (since there is a difference between the regions of my game and PS3) !!

Can someone please shed light on this matter ??

Also, please tell me if the COD4's multiplayer is a worldwide server, or a series of regional servers ? I mean, can I play COD4 multiplayer with someone in the UK or Europe, with myself located here in Pakistan (in Asia) ??

The thing is that I ahave cousins in the UK, and I wanna play COD4 multiplayer with them...would I have to purchase a EUR copy of COD4 or something ??

Thanx in advance guys :)