Hi Zakkil, welcome to the forum, you're in good hands here
About the coins you've mentioned, it sounds (to me, at least) like they could be fakes, generally the mint doesn't make errors like the writing being updside down but that is the sort of thing a counterfeiter would do. The pemember error is genuine, although not worth more than it's value really, there are just too many about. About the cleaning, please don't do it.
I'd definitely grab yourself a book on decimal coinage, you'll see an ad at the top for Rotographic books, we really can't recommend them enough. There's also a decimal section with a ton of info for general browsing, you might find some interesting stuff in there.
Get some pictures up of your best coins in the meantime, the easiest way to do it is to click bottom left (of the text box) where it says 'Drag files here to attach, or choose files...' and upload directly from your computer, once it's uploaded it will automatically show once you submit the post. If it's a size issue, get the photo up on your computer screen and take a screenshot, then crop the picture in paint and save it as a JPEG, that will get it under the 500kb limit.