Should I create separate questions for each Ubuntu version?
Should different answers be posted for each Ubuntu version?
No and No! It's the same question. Questions should not be specific to a single version and answers applying to multiple versions should be in the answers (with some additional steps to take if required). This is a lot more valuable and searchable than to have a question for this printer for every single version spread all over the site.
In case things are quite different in newer releases, a new answer could come in stating "This is how to deal with it in Cups version N since Ubuntu 12.10" and edit or comment on the other answer stating it's working until 12.04 for example. (example herehere)
Questions should not be about a single Ubuntu version in your case is my opinion. I think you should keep it to one canonical question, e.g.:
How do I get my Canon LBP-1120 printer to work?
Then in the body of such a question you indicate what you've tried, what new information you come up with by editing it, etc.
If you want it to get more attention, just put a bounty on it.