Google Fi Unlimited Plus SIM Kit

How does this work? What does the $65 go towards? Does it cover the plan fees and taxes for the first month?

If you buy just the sim, and use it for the 30 days, why do you need a US billing address? The ad says 65 credit, is that still valid as of today?

What network towers does this work with?

Will this sim work in Japan? If so will I have unlimited calls, text, and high speed data?