Conveniently, I already wrote an article to answer those first couple of questions. :)

http://waltersmith.us/newton/SELF%20and%20the%20Origins%20of...

Io is interesting to me as a sort of alternative universe version of NewtonScript. In this universe, I’m a little smarter, a little more self-confident, and I have a little more time. :) It has a strong opinion on simplicity, like Self or Smalltalk, whereas I compromised on that a bit to try to make the language seem more familiar to programmers of the Apple languages at the time, notably Pascal. It also has 100% more thought given to concurrency!

Apple was one of the originators of Unicode, so it was pretty obvious we would use it. However, we made the same mistake as Windows NT, Java, and JavaScript (and, to be fair, Unicode itself!) in thinking 16 bits would be enough and using UTF-16 to simplify the string API. Unlike the others, Newton OS didn’t survive long enough to hit that problem, though.