Ranks can't be changed for old katas with high completions

After a quick scan, I only found C, C++, coffeescript and JS to have some kind of restrictions. The way I see it, either those translations should be softened, or every other translation should be updated, but then shouldn't it be 6 kyu? Nasty situation overall :/

But why are JS tests so restrictive? Many other translations don't require any optimizations, and that makes sense for 7kyu.

Are we trying to learn to code or doing a math class?

You can choose literally every other kata to solve, you do not need to solve math kata if you do not like them :)

my answer was NOTHING like the common answer

The kata is labelled with Regex, and you chose to avoid it :P

in what world are people entering PINs like -1.234?

That's literally the point of this exercise: to validate the inputs. In the context of ATMs maybe it's not so accurate (probably impossible), but from 3rd example in description it should be clear that theoretically any data could be in input.

I do not believe this is 7kyu

It seems fine for 7kyu, especially if you use regex.