Heyo! I sent a reply to your message but just in case anyone else needs it, M is triple decrease and W is triple increase, so they’re like A and V but with 1 more stitch. Similarly, if you see something like FW, that means you do 3 double crochets into 1 stitch.
I’m not sure what MR since since I don’t think I’ve seen it before, but it could just be magic ring, depending on where you might have seen it.
And there’s no difference between X and x, since uppercase and lowercase don’t make a different. Similarly, you might see t, f, e, instead of T, F, E, but they’re the same thing. Uppercase just makes the letters look more like the crochet diagram symbol. Hope this helps!
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