That’s a lot of questions! Let’s see if I can quickly address the main issues.
Living expenses do indeed vary from one place to another, even within the same country. Some people suggest that Basic Income should vary from one area to another. Another possibility is that if you can’t afford to live in an expensive area, you’ll just have to move to a less expensive area — or get a better-paid job.
Every resident citizen would be entitled to a Basic Income. Children, however, may get a lower rate than adults.
Some people do of course need more food than others — so some people who eat very little may indeed get a little more money than they require. That, however, is no different from the situation with most existing welfare schemes.
Basic Income would not depend on how much money you earn. If you earn a lot of money, however, you will likely have to pay a lot extra in tax.
Basic Income doesn’t involve individual means testing — and this is what drastically reduces bureaucracy requirements in comparison to most existing welfare schemes.
I hope that answers your main queries.