The Playstation Network was down during April -Jun 2011 and is now back up worldwide
It is possible to do, but would need a seperate memory card from the one used to access the US PSN store.
No, a Japanese PSN account can only be funded with a Japanese PSN card, one with a yen amount on it.
It's actually known as a PSN ID. http://www.us.playstation.com/PSN/mediago
You can't. PSN stands for PlayStation Network. You can't connect a DS to PSN.
WHAT DOES PSN STAND FOR OR MEAN
by PSN you need a account to PSN
The PSP-3000 can access the PSN, yes.
No, PSN is free and there is no indication that is going to change.
Yes, there is a PSN link on the Vita's LiveArea.
The password is whatever you set it as when you registered your PSN account.
System activation is where you log onto your PSN account on a PC, and register your devices (PS3, PSP, PSVita). Only systems you have activated in this way can log into your PSN account and use your PSN data.
make a new psn user and and go to the place where you sign in on psn and it will say sign up for playstation network.