Taking a step back for a moment, if you have so many declined flags that you are getting familiar with particular decline reasons, you are probably flagging too many things!
It is good to flag when you see an obvious and prominent problem, but only if you are 99% sure that it's something that's going to help the moderators do their job.
Just as a reference point - in my time here, I have flagged more than 40 things, and only one was declined.
What do each of the four messages mean?
All the messages are very general, so I would recommend looking at each message in the context of the particular declined flag and trying to understand what the moderator was trying to tell you. For example, if you saw "Declined - flags should not be used to indicate technical inaccuracies, or an altogether wrong answer", perhaps it's because you raised a flag on something that (in the moderator's opinion) wasn't an obviously wrong answer.
Sometimes these things will be a matter of opinion. The question to ask yourself is "Am I really helping the moderators by flagging this?"