No, a Japanese PSN account can only be funded with a Japanese PSN card, one with a yen amount on it.
No, PSN cards can be used only once. If are from a different region and you need a PSN card that belongs to a different region since you have a different region account then you can buy the PSN card from online
You sign into your account and input the Playstation Network Card Number into the redeem code box
PSN only accept Credit Card or Debit Card that belongs to the region in which the PSN account was created. If you have a US PSN account then you can use only US credit or debit card.This is because PSN does some background check called Address verification Check which is basically Sony checking with your card issuing bank about the address, if the address is from a different region then you will not be able to use that card for that account.Other alternative is to use PSN cards. If you are from a different region and you use a different region PSN account then the best option is to buy a PSN card online.More detail on this can be found at : http://invisibleknight.blogspot.com/2013/04/psn-cards-playstation-network-cards-how.html
yes they can i think
A PlayStation Network Card Code is the code on the back of a card that has PSN money on it. You can use it to buy games or other things on PSN.
No, to redeem the Japanese PSN card you need to be signed into the Japanese PSN.
Well you need PSN credit, and there are two ways to do this: 1. Go to a place where they sell PSN cards (GameStop), scratch off the bottom back of the card with a coin, go to PSN, on the top right of the PSN click redeem codes, input the code that the card you bought has and whatever you payed for the card you will have on PSN. 2. You can pay by credit card.
It costs the amount of the card $20 for a $20 PSN card
by psn i assume you mean play station network, and no it wont as the PSN is free, however it could if you are buying something.
yes
No you don't need it. That is the normal way to add money to your account or you can purchase the PlayStation network card and this is quoted about the card from related link: "The PlayStation®Network Card (PSN Card) is a prepaid card that may be used to apply funds to a PlayStation®Wallet without using a credit card. Please visit your local authorized PlayStation®retailer to purchase the PSN Card."