Why have I been knocked down from level 7 to level 5 without any notification! or reason? many strange things are happening with Yahoo!?

According to your profile you have 7394 points which would be level 5, minimum 5,000 points the minimum for level 7 is 25,000, possibly there is a glitch and it isn't showing all your points.
Check the link.
https://answers.yahoo.com/info/scoring_system

This has been happening to users who keep moving others Qs to the wrong category,have you been doing that?

Yahoo has been knocking L7's down a level or two if they abuse their ability to move other people's questions and they will not send a notification of their action; at least, this is what's been said by those it's happened to. If you've been doing this, then this is likely what happened.

Having said this, if you haven't been doing this, then it's yet another glitch in a very glitchy system.

This happens when high level long time users see porn.racist
nastiness or cussing.They try helping so they report along with a few friends.then they see the post still there.
so to HELP rid the site of child porn racist hate etc,they move it.
Immediately it is deleted which makes this site useful.
You got violated DUDE.