Hi Nico,
Nothing. If a question is not answered, nothing happens. The community leaders are asked to try to answer all the questions, but as the Community has grown, and we've all got other things to do, we don't. I don't know how the others work, but I do try to run a search for unanswered questions when I have time to try to answer them, but the volume of new questions now means I rarely run that search more than once a month.
Kudos is earned by interacting with the community, but also by others rewarding you (marking an answer right, or directly handing you kudos). It's a bit more sophisticated than that brief description, but that's the core of it - being active in the community is the whole point of it
Deletion of questions, answers and comments is limited to some of the moderator levels. We had a massive problem on the platform before last where people would delete their answer or comment and render the entire conversation utterly useless. It's not ideal to block it, people should be able to delete their own content, but it's not right to let them do it without considering the contributions of others in the conversation. In my ideal system, I'd let people delete any post they'd made before it gets any (public) response. At the moment, people either edit stuff to blank it out (moderators can see a posts history, but no-one else can), or report their own "abuse". Again, less than ideal, but when the mods see either of those, they do try to move it to a non-public "consider permanent delete" bin
Yes, votes and likes count.