Answering the second question: you won't want to use it in production, but if you have ever been intrigued by one of those Unix philosophy preaches, you should definitely take a look at it. It takes the tool philosophy (build simple tools that are easy to combine) and filesystem metaphor much further, besides addressing some (albeit not all) long-standing Unix WTFs.
Plan 9 is not the most elegant design of OSes, but its simple ways of combing primitives are pretty amazing. Simplicity is underappreciated nowadays.
plan 9 is the earlier effort of re-engineering Unix and runs on hardware. It was meant to replace Unix, but it never did.
With inferno they went the VM route (the dis VM) and built it so that it runs on myriad platforms, from Unix and ActiveX. It still runs on hardware though. The intension was that you can run a network of hosted and native inferno installations, making it easier to adopt. Unfortunately, inferno saw no widespread adoption either.
The underlying filesystem concept is basically the same (the latest version of 9p and Styx are identical), but the programming environment changed a lot (you write limbo to run on dis). Also the user space programs were rewritten and get overhauled a bit. The community never get divergent enough though; inferno people tend to identify themselves as part of the plan 9 community.
Most of the team? I only know that Rob Pike and Russ Cox are Google employers. And I have the impression that they are working mostly on Golang and some distributed infrastructures. Did they employ any other inferno developers?
The beauty of the Pi is the fact you can have a variety of SD cards with different OS/Configurations and easily swap between them and play with them.
It is a very cheap educational tool. I have 4 of them, and they also make great network storage tools. Add a HDD, the transmission software and you can easily download TV shows and stream them to you 1080p TV for example. £27 in the UK, absolute bargain.