DSi hacking question

Hello,

I'm completly new to the DSi hacking scene. I'm a little bit confused because the official DSi hacking guide has no tutorial for installing cfw neither use Flipnote as a hacking entrypoint... Furthermore I would like to ask whether it is possible to hack a Japanese DSi and whether there is already a complete tutorial for installing cfw? Can I use Sudoku hax from a European 3DS (B9S) and transfer it to my Japanese DSi?
Can I still buy Sudoku DSi Ware App on European eShop (3DS)?

What...

DSi hacking question