Universal symbols for molar mass, molarity, and molality

This is a really basic (perhaps trivial) question, but I just want to confirm:

What are the SI symbols for molar mass, molarity, and molality? For molality and molarity, there is a difference, but I’ve found that the symbol is the same for molarity and molar mass, i.e. M (a big m).

Also, what are the meaningful differences between molarity and molality? Does it just have to do with mass (i.e. difference in mass between solute and solvent) vs. concentration (i.e. within the solution)?

I get the sense that molarity is defunct? I read this here -

https://www.nist.gov/pml/special-publication-811/nist-guide-si-chapter-8