a) you should not be the owner (to avoid pet projects that are not actually useful) of the project or at least not the sole owner
b) ideally it should be some high impact projects that have little to no corpo sponsors as opposed to something like React
c) if your contribution is not merged in, it should not count as "work done"
I highly disagree with this. Sometimes someone has to do the work to discover that isn't the work that should be done. As an example, last week, I got in a fight with the Go scheduler: https://github.com/php/frankenphp/pull/2016 -- in the end, we were able to find the one-liner that is a happy-medium. I didn't open that PR, but I did the work; if that makes sense.