It will advise you that certain functions of the PSVita require a PSN account, and will say you can set one up another time and link it in the Settings menu.
Games are linked to the PSN account so that's not possible.
You only need a PSN account not a new one
Yes, there is a PSN link on the Vita's LiveArea.
The PSVita's default language is based on the region your PSN account is under.
Owning a PSN account doesn't cost any money, and there are many free things on the PSN that you can take advantage of.
Technically yes you can. Your PSN account is a Sony-wide service regardless of the device you are using it on. You can redeem a PS3 code while on the PSVita's own PSN 'app', and it will be added to your PSN account. However of course, that will not let you use the PS3 content on the PSVita.
There's no Naruto games on the PSN store
Your trophies are recorded on your PSN profile, which you will log into on both your PS3 and your PSVita. On the PSVita you've got the option to just see the local trophies, the PSVita ones, but also the option to check your PSN account, which will show your PS3 trophies too.
No, a Japanese PSN account can only be funded with a Japanese PSN card, one with a yen amount on it.
The PSN is already out. It has been out ever since PS3 was released. You can access it from your PS3, PSP, or PS vita by creating a free account and logging it.
I think so because on the PS3 it is.
Yes, Angry Birds is available on PSN in a PS Vita compatible form.