Asking duplicate questions are not against the site rules. ( http://blog.stackoverflow.com/2010/11/dr-strangedupe-or-how-i-learned-to-stop-worrying-and-love-duplication/ ) Asking exact duplicates, don't using the search function are also not against the rules, just very impolite and lazy. And a lot of users even if they use the search function won't find that their question already have an answer: Users don't have the same "searching skill", some people are just bad at searching.
Answering dupes are again not against the rules. When you see a question and you know the answer to the question you won't start searching the whole site whether it has been asked before. You just answer it. After that if you feel that the question is might be a duplicate you may start searching for a dupe. Normally someone would only start by flagging a question as duplicate if he already saw that question here before, and this means only frequent users of this site will do that.
Asking EOL is off-topic and against the rules. Answering them... I don't think that it is against the rules, I've never read it anywhere that if you know the answer to an off-topic question you shouldn't answer it. If you have the time to write an answer, and don't care about that you won't get much rep for your answer (since upvotes on closed off-topics are rare.) you can answer it. Why not help if you can and you want to? Of course you should flag the question for closure as off-topic.
Not flagging is not against the rules. Flagging is not a must, it is a possibility to help the community.
"Don't tell new users about EOL rules". That's again not a must and not in the rules.
So to sum up: The problem with these users is not that they are not following the rules, because they are following them. The problem is just that they are not participate as actively as other users. Someone like spending 2-3-5 hours daily on this site, some users don't. You/We can't do anything with this other than giving incentives (badges/reputation) for more active participation.
Look, in my country, the gov tried to make it illegal to drive without using the safety belt, they tried to fine everyone who doesn't follow the law. There's another law that forbids smoking in closed places
There was a tiny problem, 85% of the population doesn't care about what the gov says, so the laws are there, but they're dead, there's not enough police to catch everyone
This is totally unrelated to this problem, but it is not a problem of the government or the police that most of the people in your country are dumb and don't care about their life. This is a problem in the society.
EDIT: I see you've just edited out most of your question I was reflecting to before I posted my answer. But I will leave my answer as it is, because I think it is still relevant.