1: Yes, the game will recognize it's Japanese.
2: Yes, they will still be shiny.
3: Yeah, trading them between Sun and Moon will work just fine.
4: Yes, you still need to pay, and you pay as soon as you open the software for the first time, before you can access any of the features.
5: There is no way to cancel the subscription, so once you pay the $5, you have a full 365 days to use the software however you please until your subscription ends.
6: As soon as you finish paying, you should get charged to your credit/debit card automatically. And as far as I've seen, I've never got any emails from the software, and I've been using Bank for quite some time.
If you have any other Bank questions, just let me know!