Closed is the same as your "frozen". The idea behind closing a question is to prevent answers to a question that is not a good fit for Programmers (or, more generally, to the Stack Exchange format). Closed is meant as a temporary state. Either the question gets sufficient corrections and reopened or it can't be salvaged and gets deleted. There are even some automatic procedures in place to clean up some questions.
Closing early (as in before any answers have been posted) is a very good thing. It enables people (preferably the author, otherwise the community members) to fix the question and make it a good question. Once there are answers, it takes more work to make the question good, since edits will either have to be sure to not invalidate any existing answers or the community will also have to clean up the existing answers to make them valid (otherwise, a moderator would have to delete them).
There are also two other states for questions - protected and locked. Protected questions can not be answered by users who have not hit a reputation threshold. Locked questions are to resolve extremely serious problems and prevent all voting and editing (and for questions, new answers) and provides for questions that are being discussed on Meta, questions that have historical significance but are not good questions, or have generated a large number of off-topic or chatty comments.
If you're trying to save old questions, go through the list of closed questions. If you see a question that you don't think should have been closed, ask about the reasoning in Chat or on Meta. If you can save it, make a heroic edit, clean it up, and vote to reopen (and maybe share your work on chat to get more feedback, edits, and reopen votes).
From my perspective as a moderator, I rarely see flags to reopen a closed question. If you make a heroic edit and aren't getting reopen votes, flag it for review by a moderator.
However, something that we haven't been doing (and perhaps should consider) is looking at the old closed questions that don't meet the criteria for automatic deletion and either salvaging them or deleting them. However, that would need to be a new discussion.