None of this is enforced at the tools level.
The prefix wouldn't necessarily be only a single character. For example, using a "p" prefix for pointer values was a common convention in Microsoft ecosystem projects where Hungarian notation was probably most popular. Thus a pointer-to-char (char*) parameter might be prefixed with "pc".
But yes, the fundamental idea was to convey information about the type of the variable as part of its name. That convention has mostly died out today, probably due to a combination of IDEs being used routinely in the ecosystem where the notation was most popular, and more recently due to modern languages having better type systems that enforce the rules objectively instead of relying on a convention.
Ironically, with the popularity of dynamically typed languages today, we sometimes seem to have regressed to a point where interfaces to functions aren't always clear, and lots of avoidable bugs creep in due to passing incorrect types of data around. The emphasis on rapid evolution and ad-hoc/organic design we see with a lot of "agile" development processes isn't always helpful either. Put those together, and you almost have the complete opposite of the systematic design and robust processes advocated in the slides here.
No.
There are two types of Hungarian Notation.
The original one ("apps hungarian"), which made sense and sometimes still makes sense. Here you would assign a meaning to a prefix. For example, if you're writing MS Word a variable named "sWidth" might be the width of something in pixels on the screen (s), while "pWidth" might be the same width, but in logical units (say pt) on the page. Then you could have a function ptos, and it's easy to see whether variables were used correctly in computations - you can't mix screen-space and page-space coordinates without conversion.
This made a lot of sense, because either variable would likely just be an "int".
Similarly in a Python Webapp one might write "us_name" where us means UnSanitized. So before passing that anywhere else you know you need to sanitize it. See a "us_" variable somewhere that isn't a call to a sanitizer? Probably a bug!
Then there's that other one, "system hungarian", which is the stupid thing everyone knows with stuff like lpcstrWindowName.
EDIT: people often see these as prefixes, but they are not really prefixes, the original paper was about the whole name.
In modern languages where defining custom types and enforcing their use is easier, there is less need to distinguish these properties by convention. Twenty years ago, when we were doing more development with languages in the C family that don't have very powerful systems, it was a different story, and so naming conventions went some way to helping keep track of what data you were really passing around beyond just "It's an int" and the like.
It's just that nobody ever actually does that in C++.
This is, after all, exactly how systems hungarian misunderstanding came about.
sh-i-sh-k-eb-ab-----
I can see it!
Choo-Choo-Train
I can see it!
So, carry on...